# Ex 13.5, 15 (MCQ) - Chapter 13 Class 12 Probability (Term 2)

Last updated at Aug. 11, 2021 by Teachoo

Ex 13.5

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Ex 13.5, 14 (MCQ) Important Deleted for CBSE Board 2022 Exams

Ex 13.5, 15 (MCQ) Important Deleted for CBSE Board 2022 Exams You are here

Chapter 13 Class 12 Probability (Term 2)

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Last updated at Aug. 11, 2021 by Teachoo

Ex 13.5, 15 The probability that a student is not a swimmer is 1/5 . Then the probability that out of five students, four are swimmers is (A) 5C4 (4/5)^4 1/5 (B) (4/5)^4 1/5 (C) 5C1 1/5 (4/5)^4 (D) None of theseIf a trial is Bernoulli, then There is finite number of trials They are independent Trial has 2 outcomes i.e. Probability success = P then Probability failure = q = 1 β P (4) Probability of success (p) is same for all trials Let X : be number of swimmers Picking a student is a Bernoulli trial So, X has binomial distribution P(X = x) = nCx π^(πβπ) π^π Here, n = number of students = 5 Given probability that student is not a swimmer is 1/5 So, q = 1/5 β΄ p = 1 β q = 1 β 1/5 = 4/5 Hence, P(X = x) = 5Cx (π/π)^π (π/π)^(π β π) We need to find the Probability of that out of five students, four are swimmers i.e. P(X = 4) P(X = 4) = 5C4 (4/5)^4 (1/5)^(5 β 4) = 5C4 (π/π)^π π/π = 5C1 π/π (π/π)^π Hence, option (A) & (C) both are correct