A Quiz Consists Of 20 Multiple-choice Questions, Each With 5 Possible Answers. For Someone Who Makes Random Guesses For All Of The Answers, Find The Probability Of Passing If The Minimum Passing Grade Is 60 % 60\% 60% . Given: $P(\text{pass}) =

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Introduction


In this article, we will explore the concept of probability and its application in a multiple-choice quiz scenario. A quiz consists of 20 multiple-choice questions, each with 5 possible answers. We will calculate the probability of passing the quiz if the minimum passing grade is 60%60\% and the individual makes random guesses for all of the answers.

Understanding the Problem


To begin with, let's understand the problem at hand. We have a quiz with 20 multiple-choice questions, each with 5 possible answers. This means that for each question, there are 5 possible outcomes, and the individual making random guesses has an equal chance of selecting any of the 5 options.

Calculating the Probability of Passing


To calculate the probability of passing the quiz, we need to determine the number of correct answers required to achieve a minimum passing grade of 60%60\%. Since there are 20 questions in the quiz, the minimum passing grade of 60%60\% corresponds to 12 correct answers (20 x 0.6 = 12).

Probability of Getting a Single Question Correct


Now, let's calculate the probability of getting a single question correct. Since there are 5 possible answers, the probability of selecting the correct answer is 1 out of 5, which is 15\frac{1}{5} or 0.2.

Probability of Getting a Single Question Incorrect


Similarly, the probability of getting a single question incorrect is 4 out of 5, which is 45\frac{4}{5} or 0.8.

Probability of Getting Exactly 12 Questions Correct


To calculate the probability of getting exactly 12 questions correct, we need to use the binomial probability formula. The binomial probability formula is given by:

P(X=k)=(nk)pk(1βˆ’p)nβˆ’kP(X = k) = \binom{n}{k} p^k (1-p)^{n-k}

where nn is the number of trials, kk is the number of successes, pp is the probability of success, and (nk)\binom{n}{k} is the binomial coefficient.

In this case, n=20n = 20, k=12k = 12, and p=0.2p = 0.2. Plugging these values into the formula, we get:

P(X=12)=(2012)(0.2)12(0.8)8P(X = 12) = \binom{20}{12} (0.2)^{12} (0.8)^{8}

Calculating the Binomial Coefficient


The binomial coefficient (2012)\binom{20}{12} can be calculated using the formula:

(nk)=n!k!(nβˆ’k)!\binom{n}{k} = \frac{n!}{k!(n-k)!}

where n!n! is the factorial of nn. Plugging in the values, we get:

(2012)=20!12!(20βˆ’12)!=20!12!8!\binom{20}{12} = \frac{20!}{12!(20-12)!} = \frac{20!}{12!8!}

Evaluating the Factorials


To evaluate the factorials, we can use the following formula:

n!=nΓ—(nβˆ’1)Γ—(nβˆ’2)×…×2Γ—1n! = n \times (n-1) \times (n-2) \times \ldots \times 2 \times 1

Plugging in the values, we get:

20!=20Γ—19Γ—18×…×2Γ—120! = 20 \times 19 \times 18 \times \ldots \times 2 \times 1

12!=12Γ—11Γ—10×…×2Γ—112! = 12 \times 11 \times 10 \times \ldots \times 2 \times 1

8!=8Γ—7Γ—6×…×2Γ—18! = 8 \times 7 \times 6 \times \ldots \times 2 \times 1

Calculating the Binomial Coefficient


Now that we have evaluated the factorials, we can calculate the binomial coefficient:

(2012)=20!12!8!=2432902008176640000479001600=125970\binom{20}{12} = \frac{20!}{12!8!} = \frac{2432902008176640000}{479001600} = 125970

Calculating the Probability of Getting Exactly 12 Questions Correct


Now that we have calculated the binomial coefficient, we can calculate the probability of getting exactly 12 questions correct:

P(X=12)=(2012)(0.2)12(0.8)8=125970Γ—(0.2)12Γ—(0.8)8P(X = 12) = \binom{20}{12} (0.2)^{12} (0.8)^{8} = 125970 \times (0.2)^{12} \times (0.8)^{8}

Evaluating the Exponents


To evaluate the exponents, we can use the following formula:

ab=aΓ—a×…×a⏟bΒ timesa^b = \underbrace{a \times a \times \ldots \times a}_{b \text{ times}}

Plugging in the values, we get:

(0.2)12=0.2Γ—0.2×…×0.2Β (12Β times)(0.2)^{12} = 0.2 \times 0.2 \times \ldots \times 0.2 \text{ (12 times)}

(0.8)8=0.8Γ—0.8×…×0.8Β (8Β times)(0.8)^{8} = 0.8 \times 0.8 \times \ldots \times 0.8 \text{ (8 times)}

Calculating the Probability of Getting Exactly 12 Questions Correct


Now that we have evaluated the exponents, we can calculate the probability of getting exactly 12 questions correct:

P(X = 12) = 125970 \times (0.2)^{12} \times (0.8)^{8} = 125970 \times 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000<br/> # A Quiz with Random Guesses: Calculating the Probability of Passing ===========================================================

Q&A: Calculating the Probability of Passing a Quiz with Random Guesses


Q: What is the probability of passing a quiz with 20 multiple-choice questions, each with 5 possible answers, if the minimum passing grade is 60%60\% and the individual makes random guesses for all of the answers?

A: To calculate the probability of passing the quiz, we need to determine the number of correct answers required to achieve a minimum passing grade of 60%60\%. Since there are 20 questions in the quiz, the minimum passing grade of 60%60\% corresponds to 12 correct answers (20 x 0.6 = 12).

Q: What is the probability of getting a single question correct?

A: Since there are 5 possible answers, the probability of selecting the correct answer is 1 out of 5, which is 15\frac{1}{5} or 0.2.

Q: What is the probability of getting a single question incorrect?

A: Similarly, the probability of getting a single question incorrect is 4 out of 5, which is 45\frac{4}{5} or 0.8.

Q: How do we calculate the probability of getting exactly 12 questions correct?

A: To calculate the probability of getting exactly 12 questions correct, we need to use the binomial probability formula. The binomial probability formula is given by:

P(X=k)=(nk)pk(1βˆ’p)nβˆ’k</span></p><p>where<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi></mrow><annotationencoding="application/xβˆ’tex">n</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">n</span></span></span></span>isthenumberoftrials,<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi></mrow><annotationencoding="application/xβˆ’tex">k</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal"style="marginβˆ’right:0.03148em;">k</span></span></span></span>isthenumberofsuccesses,<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotationencoding="application/xβˆ’tex">p</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.625em;verticalβˆ’align:βˆ’0.1944em;"></span><spanclass="mordmathnormal">p</span></span></span></span>istheprobabilityofsuccess,and<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mi>n</mi><mi>k</mi></mfrac><mofence="true">)</mo></mrow><annotationencoding="application/xβˆ’tex">(nk)</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1.2em;verticalβˆ’align:βˆ’0.35em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize1">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.7454em;"><spanstyle="top:βˆ’2.355em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmathnormalmtight"style="marginβˆ’right:0.03148em;">k</span></span></span></span><spanstyle="top:βˆ’3.144em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmathnormalmtight">n</span></span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.345em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize1">)</span></span></span></span></span></span>isthebinomialcoefficient.</p><h3>Q:Whatisthebinomialcoefficient<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><annotationencoding="application/xβˆ’tex">(2012)</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1.2451em;verticalβˆ’align:βˆ’0.35em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize1">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8951em;"><spanstyle="top:βˆ’2.355em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span><spanstyle="top:βˆ’3.144em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">20</span></span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.345em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize1">)</span></span></span></span></span></span>?</h3><h3>A:Thebinomialcoefficient<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><annotationencoding="application/xβˆ’tex">(2012)</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1.2451em;verticalβˆ’align:βˆ’0.35em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize1">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8951em;"><spanstyle="top:βˆ’2.355em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span><spanstyle="top:βˆ’3.144em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">20</span></span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.345em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize1">)</span></span></span></span></span></span>canbecalculatedusingtheformula:</h3><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mi>n</mi><mi>k</mi></mfrac><mofence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mi>n</mi><mostretchy="false">!</mo></mrow><mrow><mi>k</mi><mostretchy="false">!</mo><mostretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mi>k</mi><mostretchy="false">)</mo><mostretchy="false">!</mo></mrow></mfrac></mrow><annotationencoding="application/xβˆ’tex">(nk)=n!k!(nβˆ’k)!</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:2.4em;verticalβˆ’align:βˆ’0.95em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize3">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.1076em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mordmathnormal"style="marginβˆ’right:0.03148em;">k</span></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mordmathnormal">n</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize3">)</span></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.3074em;verticalβˆ’align:βˆ’0.936em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3714em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mordmathnormal"style="marginβˆ’right:0.03148em;">k</span><spanclass="mclose">!</span><spanclass="mopen">(</span><spanclass="mordmathnormal">n</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">βˆ’</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mordmathnormal"style="marginβˆ’right:0.03148em;">k</span><spanclass="mclose">)!</span></span></span><spanstyle="top:βˆ’3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="fracβˆ’line"style="borderβˆ’bottomβˆ’width:0.04em;"></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mordmathnormal">n</span><spanclass="mclose">!</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.936em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span></span></span></span></span></p><p>where<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><mostretchy="false">!</mo></mrow><annotationencoding="application/xβˆ’tex">n!</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">n</span><spanclass="mclose">!</span></span></span></span>isthefactorialof<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi></mrow><annotationencoding="application/xβˆ’tex">n</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">n</span></span></span></span>.Plugginginthevalues,weget:</p><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mn>20</mn><mostretchy="false">!</mo></mrow><mrow><mn>12</mn><mostretchy="false">!</mo><mostretchy="false">(</mo><mn>20</mn><mo>βˆ’</mo><mn>12</mn><mostretchy="false">)</mo><mostretchy="false">!</mo></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>20</mn><mostretchy="false">!</mo></mrow><mrow><mn>12</mn><mostretchy="false">!</mo><mn>8</mn><mostretchy="false">!</mo></mrow></mfrac></mrow><annotationencoding="application/xβˆ’tex">(2012)=20!12!(20βˆ’12)!=20!12!8!</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:2.4em;verticalβˆ’align:βˆ’0.95em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize3">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize3">)</span></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.3074em;verticalβˆ’align:βˆ’0.936em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3714em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span><spanclass="mclose">!</span><spanclass="mopen">(</span><spanclass="mord">20</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">βˆ’</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mord">12</span><spanclass="mclose">)!</span></span></span><spanstyle="top:βˆ’3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="fracβˆ’line"style="borderβˆ’bottomβˆ’width:0.04em;"></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span><spanclass="mclose">!</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.936em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.0574em;verticalβˆ’align:βˆ’0.686em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3714em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span><spanclass="mclose">!</span><spanclass="mord">8</span><spanclass="mclose">!</span></span></span><spanstyle="top:βˆ’3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="fracβˆ’line"style="borderβˆ’bottomβˆ’width:0.04em;"></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span><spanclass="mclose">!</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span></span></span></span></span></p><h3>Q:Howdoweevaluatethefactorials?</h3><h3>A:Toevaluatethefactorials,wecanusethefollowingformula:</h3><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mi>n</mi><mostretchy="false">!</mo><mo>=</mo><mi>n</mi><mo>Γ—</mo><mostretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mn>1</mn><mostretchy="false">)</mo><mo>Γ—</mo><mostretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mn>2</mn><mostretchy="false">)</mo><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotationencoding="application/xβˆ’tex">n!=nΓ—(nβˆ’1)Γ—(nβˆ’2)×…×2Γ—1</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">n</span><spanclass="mclose">!</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6667em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mordmathnormal">n</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mordmathnormal">n</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">βˆ’</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mord">1</span><spanclass="mclose">)</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mordmathnormal">n</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">βˆ’</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mord">2</span><spanclass="mclose">)</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6667em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="minner">…</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">2</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">1</span></span></span></span></span></p><p>Plugginginthevalues,weget:</p><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mn>20</mn><mostretchy="false">!</mo><mo>=</mo><mn>20</mn><mo>Γ—</mo><mn>19</mn><mo>Γ—</mo><mn>18</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotationencoding="application/xβˆ’tex">20!=20Γ—19Γ—18×…×2Γ—1</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mord">20</span><spanclass="mclose">!</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">20</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">19</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">18</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6667em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="minner">…</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">2</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">1</span></span></span></span></span></p><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mn>12</mn><mostretchy="false">!</mo><mo>=</mo><mn>12</mn><mo>Γ—</mo><mn>11</mn><mo>Γ—</mo><mn>10</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotationencoding="application/xβˆ’tex">12!=12Γ—11Γ—10×…×2Γ—1</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mord">12</span><spanclass="mclose">!</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">12</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">11</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">10</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6667em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="minner">…</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">2</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">1</span></span></span></span></span></p><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mn>8</mn><mostretchy="false">!</mo><mo>=</mo><mn>8</mn><mo>Γ—</mo><mn>7</mn><mo>Γ—</mo><mn>6</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotationencoding="application/xβˆ’tex">8!=8Γ—7Γ—6×…×2Γ—1</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mord">8</span><spanclass="mclose">!</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">8</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">7</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">6</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6667em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="minner">…</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">2</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">1</span></span></span></span></span></p><h3>Q:Whatisthevalueofthebinomialcoefficient<spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><annotationencoding="application/xβˆ’tex">(2012)</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1.2451em;verticalβˆ’align:βˆ’0.35em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize1">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8951em;"><spanstyle="top:βˆ’2.355em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span><spanstyle="top:βˆ’3.144em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">20</span></span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.345em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize1">)</span></span></span></span></span></span>?</h3><h3>A:Nowthatwehaveevaluatedthefactorials,wecancalculatethebinomialcoefficient:</h3><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mn>20</mn><mostretchy="false">!</mo></mrow><mrow><mn>12</mn><mostretchy="false">!</mo><mn>8</mn><mostretchy="false">!</mo></mrow></mfrac><mo>=</mo><mfrac><mn>2432902008176640000</mn><mn>479001600</mn></mfrac><mo>=</mo><mn>125970</mn></mrow><annotationencoding="application/xβˆ’tex">(2012)=20!12!8!=2432902008176640000479001600=125970</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:2.4em;verticalβˆ’align:βˆ’0.95em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize3">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize3">)</span></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.0574em;verticalβˆ’align:βˆ’0.686em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3714em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span><spanclass="mclose">!</span><spanclass="mord">8</span><spanclass="mclose">!</span></span></span><spanstyle="top:βˆ’3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="fracβˆ’line"style="borderβˆ’bottomβˆ’width:0.04em;"></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span><spanclass="mclose">!</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.0074em;verticalβˆ’align:βˆ’0.686em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">479001600</span></span></span><spanstyle="top:βˆ’3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="fracβˆ’line"style="borderβˆ’bottomβˆ’width:0.04em;"></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">2432902008176640000</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">125970</span></span></span></span></span></p><h3>Q:Howdowecalculatetheprobabilityofgettingexactly12questionscorrect?</h3><h3>A:Nowthatwehavecalculatedthebinomialcoefficient,wecancalculatetheprobabilityofgettingexactly12questionscorrect:</h3><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mi>P</mi><mostretchy="false">(</mo><mi>X</mi><mo>=</mo><mn>12</mn><mostretchy="false">)</mo><mo>=</mo><mrow><mofence="true">(</mo><mfraclinethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mofence="true">)</mo></mrow><mostretchy="false">(</mo><mn>0.2</mn><msup><mostretchy="false">)</mo><mn>12</mn></msup><mostretchy="false">(</mo><mn>0.8</mn><msup><mostretchy="false">)</mo><mn>8</mn></msup><mo>=</mo><mn>125970</mn><mo>Γ—</mo><mostretchy="false">(</mo><mn>0.2</mn><msup><mostretchy="false">)</mo><mn>12</mn></msup><mo>Γ—</mo><mostretchy="false">(</mo><mn>0.8</mn><msup><mostretchy="false">)</mo><mn>8</mn></msup></mrow><annotationencoding="application/xβˆ’tex">P(X=12)=(2012)(0.2)12(0.8)8=125970Γ—(0.2)12Γ—(0.8)8</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mordmathnormal"style="marginβˆ’right:0.13889em;">P</span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="marginβˆ’right:0.07847em;">X</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mord">12</span><spanclass="mclose">)</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.4em;verticalβˆ’align:βˆ’0.95em;"></span><spanclass="mord"><spanclass="mopendelimcenter"style="top:0em;"><spanclass="delimsizingsize3">(</span></span><spanclass="mfrac"><spanclass="vlistβˆ’tvlistβˆ’t2"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:βˆ’2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">12</span></span></span><spanstyle="top:βˆ’3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">20</span></span></span></span><spanclass="vlistβˆ’s">​</span></span><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosedelimcenter"style="top:0em;"><spanclass="delimsizingsize3">)</span></span></span><spanclass="mopen">(</span><spanclass="mord">0.2</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span></span></span></span></span></span><spanclass="mopen">(</span><spanclass="mord">0.8</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">8</span></span></span></span></span></span></span></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">125970</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mord">0.2</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span></span></span></span></span></span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mord">0.8</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">8</span></span></span></span></span></span></span></span></span></span></span></span></span></p><h3>Q:Whatisthevalueoftheprobabilityofgettingexactly12questionscorrect?</h3><h3>A:Nowthatwehaveevaluatedtheexponents,wecancalculatetheprobabilityofgettingexactly12questionscorrect:</h3><pclass=β€²katexβˆ’blockβ€²><spanclass="katexβˆ’display"><spanclass="katex"><spanclass="katexβˆ’mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mi>P</mi><mostretchy="false">(</mo><mi>X</mi><mo>=</mo><mn>12</mn><mostretchy="false">)</mo><mo>=</mo><mn>125970</mn><mo>Γ—</mo><mostretchy="false">(</mo><mn>0.2</mn><msup><mostretchy="false">)</mo><mn>12</mn></msup><mo>Γ—</mo><mostretchy="false">(</mo><mn>0.8</mn><msup><mostretchy="false">)</mo><mn>8</mn></msup><mo>=</mo><mn>0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</mn></mrow><annotationencoding="application/xβˆ’tex">P(X=12)=125970Γ—(0.2)12Γ—(0.8)8=0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</annotation></semantics></math></span><spanclass="katexβˆ’html"ariaβˆ’hidden="true"><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mordmathnormal"style="marginβˆ’right:0.13889em;">P</span><spanclass="mopen">(</span><spanclass="mordmathnormal"style="marginβˆ’right:0.07847em;">X</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mord">12</span><spanclass="mclose">)</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.7278em;verticalβˆ’align:βˆ’0.0833em;"></span><spanclass="mord">125970</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mord">0.2</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">12</span></span></span></span></span></span></span></span></span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span><spanclass="mbin">Γ—</span><spanclass="mspace"style="marginβˆ’right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;verticalβˆ’align:βˆ’0.25em;"></span><spanclass="mopen">(</span><spanclass="mord">0.8</span><spanclass="mclose"><spanclass="mclose">)</span><spanclass="msupsub"><spanclass="vlistβˆ’t"><spanclass="vlistβˆ’r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:βˆ’3.113em;marginβˆ’right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingresetβˆ’size6size3mtight"><spanclass="mordmtight"><spanclass="mordmtight">8</span></span></span></span></span></span></span></span></span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="marginβˆ’right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</span></span></span></span></span></p>P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} </span></p> <p>where <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi></mrow><annotation encoding="application/x-tex">n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal">n</span></span></span></span> is the number of trials, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>k</mi></mrow><annotation encoding="application/x-tex">k</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span></span></span></span> is the number of successes, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi></mrow><annotation encoding="application/x-tex">p</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">p</span></span></span></span> is the probability of success, and <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mi>n</mi><mi>k</mi></mfrac><mo fence="true">)</mo></mrow><annotation encoding="application/x-tex">\binom{n}{k}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2em;vertical-align:-0.35em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size1">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.7454em;"><span style="top:-2.355em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight" style="margin-right:0.03148em;">k</span></span></span></span><span style="top:-3.144em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">n</span></span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size1">)</span></span></span></span></span></span> is the binomial coefficient.</p> <h3>Q: What is the binomial coefficient <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><annotation encoding="application/x-tex">\binom{20}{12}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2451em;vertical-align:-0.35em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size1">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8951em;"><span style="top:-2.355em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span><span style="top:-3.144em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">20</span></span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size1">)</span></span></span></span></span></span>?</h3> <h3>A: The binomial coefficient <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><annotation encoding="application/x-tex">\binom{20}{12}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2451em;vertical-align:-0.35em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size1">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8951em;"><span style="top:-2.355em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span><span style="top:-3.144em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">20</span></span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size1">)</span></span></span></span></span></span> can be calculated using the formula:</h3> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mi>n</mi><mi>k</mi></mfrac><mo fence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mi>n</mi><mo stretchy="false">!</mo></mrow><mrow><mi>k</mi><mo stretchy="false">!</mo><mo stretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mi>k</mi><mo stretchy="false">)</mo><mo stretchy="false">!</mo></mrow></mfrac></mrow><annotation encoding="application/x-tex">\binom{n}{k} = \frac{n!}{k!(n-k)!} </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:2.4em;vertical-align:-0.95em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size3">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.1076em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03148em;">k</span></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">n</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size3">)</span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.3074em;vertical-align:-0.936em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3714em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mclose">!</span><span class="mopen">(</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">βˆ’</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mclose">)!</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord mathnormal">n</span><span class="mclose">!</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.936em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span></span></span></span></p> <p>where <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><mo stretchy="false">!</mo></mrow><annotation encoding="application/x-tex">n!</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">n</span><span class="mclose">!</span></span></span></span> is the factorial of <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi></mrow><annotation encoding="application/x-tex">n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal">n</span></span></span></span>. Plugging in the values, we get:</p> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mn>20</mn><mo stretchy="false">!</mo></mrow><mrow><mn>12</mn><mo stretchy="false">!</mo><mo stretchy="false">(</mo><mn>20</mn><mo>βˆ’</mo><mn>12</mn><mo stretchy="false">)</mo><mo stretchy="false">!</mo></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>20</mn><mo stretchy="false">!</mo></mrow><mrow><mn>12</mn><mo stretchy="false">!</mo><mn>8</mn><mo stretchy="false">!</mo></mrow></mfrac></mrow><annotation encoding="application/x-tex">\binom{20}{12} = \frac{20!}{12!(20-12)!} = \frac{20!}{12!8!} </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:2.4em;vertical-align:-0.95em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size3">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3214em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size3">)</span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.3074em;vertical-align:-0.936em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3714em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span><span class="mclose">!</span><span class="mopen">(</span><span class="mord">20</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">βˆ’</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mord">12</span><span class="mclose">)!</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span><span class="mclose">!</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.936em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.0574em;vertical-align:-0.686em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3714em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span><span class="mclose">!</span><span class="mord">8</span><span class="mclose">!</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span><span class="mclose">!</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span></span></span></span></span></p> <h3>Q: How do we evaluate the factorials?</h3> <h3>A: To evaluate the factorials, we can use the following formula:</h3> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>n</mi><mo stretchy="false">!</mo><mo>=</mo><mi>n</mi><mo>Γ—</mo><mo stretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mn>1</mn><mo stretchy="false">)</mo><mo>Γ—</mo><mo stretchy="false">(</mo><mi>n</mi><mo>βˆ’</mo><mn>2</mn><mo stretchy="false">)</mo><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotation encoding="application/x-tex">n! = n \times (n-1) \times (n-2) \times \ldots \times 2 \times 1 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">n</span><span class="mclose">!</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">βˆ’</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">1</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">βˆ’</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">2</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="minner">…</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">2</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">1</span></span></span></span></span></p> <p>Plugging in the values, we get:</p> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>20</mn><mo stretchy="false">!</mo><mo>=</mo><mn>20</mn><mo>Γ—</mo><mn>19</mn><mo>Γ—</mo><mn>18</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotation encoding="application/x-tex">20! = 20 \times 19 \times 18 \times \ldots \times 2 \times 1 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">20</span><span class="mclose">!</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">20</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">19</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">18</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="minner">…</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">2</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">1</span></span></span></span></span></p> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>12</mn><mo stretchy="false">!</mo><mo>=</mo><mn>12</mn><mo>Γ—</mo><mn>11</mn><mo>Γ—</mo><mn>10</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotation encoding="application/x-tex">12! = 12 \times 11 \times 10 \times \ldots \times 2 \times 1 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">12</span><span class="mclose">!</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">12</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">11</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">10</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="minner">…</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">2</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">1</span></span></span></span></span></p> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mn>8</mn><mo stretchy="false">!</mo><mo>=</mo><mn>8</mn><mo>Γ—</mo><mn>7</mn><mo>Γ—</mo><mn>6</mn><mo>Γ—</mo><mo>…</mo><mo>Γ—</mo><mn>2</mn><mo>Γ—</mo><mn>1</mn></mrow><annotation encoding="application/x-tex">8! = 8 \times 7 \times 6 \times \ldots \times 2 \times 1 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">8</span><span class="mclose">!</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">8</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">7</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">6</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="minner">…</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">2</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">1</span></span></span></span></span></p> <h3>Q: What is the value of the binomial coefficient <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><annotation encoding="application/x-tex">\binom{20}{12}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.2451em;vertical-align:-0.35em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size1">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8951em;"><span style="top:-2.355em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span><span style="top:-3.144em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">20</span></span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.345em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size1">)</span></span></span></span></span></span>?</h3> <h3>A: Now that we have evaluated the factorials, we can calculate the binomial coefficient:</h3> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><mo>=</mo><mfrac><mrow><mn>20</mn><mo stretchy="false">!</mo></mrow><mrow><mn>12</mn><mo stretchy="false">!</mo><mn>8</mn><mo stretchy="false">!</mo></mrow></mfrac><mo>=</mo><mfrac><mn>2432902008176640000</mn><mn>479001600</mn></mfrac><mo>=</mo><mn>125970</mn></mrow><annotation encoding="application/x-tex">\binom{20}{12} = \frac{20!}{12!8!} = \frac{2432902008176640000}{479001600} = 125970 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:2.4em;vertical-align:-0.95em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size3">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3214em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size3">)</span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.0574em;vertical-align:-0.686em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3714em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span><span class="mclose">!</span><span class="mord">8</span><span class="mclose">!</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span><span class="mclose">!</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.0074em;vertical-align:-0.686em;"></span><span class="mord"><span class="mopen nulldelimiter"></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3214em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">479001600</span></span></span><span style="top:-3.23em;"><span class="pstrut" style="height:3em;"></span><span class="frac-line" style="border-bottom-width:0.04em;"></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">2432902008176640000</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose nulldelimiter"></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">125970</span></span></span></span></span></p> <h3>Q: How do we calculate the probability of getting exactly 12 questions correct?</h3> <h3>A: Now that we have calculated the binomial coefficient, we can calculate the probability of getting exactly 12 questions correct:</h3> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>P</mi><mo stretchy="false">(</mo><mi>X</mi><mo>=</mo><mn>12</mn><mo stretchy="false">)</mo><mo>=</mo><mrow><mo fence="true">(</mo><mfrac linethickness="0px"><mn>20</mn><mn>12</mn></mfrac><mo fence="true">)</mo></mrow><mo stretchy="false">(</mo><mn>0.2</mn><msup><mo stretchy="false">)</mo><mn>12</mn></msup><mo stretchy="false">(</mo><mn>0.8</mn><msup><mo stretchy="false">)</mo><mn>8</mn></msup><mo>=</mo><mn>125970</mn><mo>Γ—</mo><mo stretchy="false">(</mo><mn>0.2</mn><msup><mo stretchy="false">)</mo><mn>12</mn></msup><mo>Γ—</mo><mo stretchy="false">(</mo><mn>0.8</mn><msup><mo stretchy="false">)</mo><mn>8</mn></msup></mrow><annotation encoding="application/x-tex">P(X = 12) = \binom{20}{12} (0.2)^{12} (0.8)^{8} = 125970 \times (0.2)^{12} \times (0.8)^{8} </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.13889em;">P</span><span class="mopen">(</span><span class="mord mathnormal" style="margin-right:0.07847em;">X</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">12</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:2.4em;vertical-align:-0.95em;"></span><span class="mord"><span class="mopen delimcenter" style="top:0em;"><span class="delimsizing size3">(</span></span><span class="mfrac"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:1.3214em;"><span style="top:-2.314em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">12</span></span></span><span style="top:-3.677em;"><span class="pstrut" style="height:3em;"></span><span class="mord"><span class="mord">20</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.686em;"><span></span></span></span></span></span><span class="mclose delimcenter" style="top:0em;"><span class="delimsizing size3">)</span></span></span><span class="mopen">(</span><span class="mord">0.2</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span></span></span></span></span></span><span class="mopen">(</span><span class="mord">0.8</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">8</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">125970</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1.1141em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord">0.2</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1.1141em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord">0.8</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">8</span></span></span></span></span></span></span></span></span></span></span></span></span></p> <h3>Q: What is the value of the probability of getting exactly 12 questions correct?</h3> <h3>A: Now that we have evaluated the exponents, we can calculate the probability of getting exactly 12 questions correct:</h3> <p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><mrow><mi>P</mi><mo stretchy="false">(</mo><mi>X</mi><mo>=</mo><mn>12</mn><mo stretchy="false">)</mo><mo>=</mo><mn>125970</mn><mo>Γ—</mo><mo stretchy="false">(</mo><mn>0.2</mn><msup><mo stretchy="false">)</mo><mn>12</mn></msup><mo>Γ—</mo><mo stretchy="false">(</mo><mn>0.8</mn><msup><mo stretchy="false">)</mo><mn>8</mn></msup><mo>=</mo><mn>0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</mn></mrow><annotation encoding="application/x-tex">P(X = 12) = 125970 \times (0.2)^{12} \times (0.8)^{8} = 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.13889em;">P</span><span class="mopen">(</span><span class="mord mathnormal" style="margin-right:0.07847em;">X</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">12</span><span class="mclose">)</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">125970</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1.1141em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord">0.2</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">12</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">Γ—</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1.1141em;vertical-align:-0.25em;"></span><span class="mopen">(</span><span class="mord">0.8</span><span class="mclose"><span class="mclose">)</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8641em;"><span style="top:-3.113em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">8</span></span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000</span></span></span></span></span></p>