Now learn Economics at Teachoo for Class 12

Ex 13.5

Ex 13.5, 1
Deleted for CBSE Board 2022 Exams

Ex 13.5, 2 Deleted for CBSE Board 2022 Exams

Ex 13.5, 3 Important Deleted for CBSE Board 2022 Exams

Ex 13.5, 4 Important Deleted for CBSE Board 2022 Exams

Ex 13.5, 5 Deleted for CBSE Board 2022 Exams

Ex 13.5, 6 Important Deleted for CBSE Board 2022 Exams

Ex 13.5, 7 Important Deleted for CBSE Board 2022 Exams You are here

Ex 13.5, 8 Deleted for CBSE Board 2022 Exams

Ex 13.5, 9 Deleted for CBSE Board 2022 Exams

Ex 13.5, 10 Important Deleted for CBSE Board 2022 Exams

Ex 13.5, 11 Deleted for CBSE Board 2022 Exams

Ex 13.5, 12 Deleted for CBSE Board 2022 Exams

Ex 13.5, 13 Important Deleted for CBSE Board 2022 Exams

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

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

Chapter 13 Class 12 Probability (Term 2)

Serial order wise

Last updated at Feb. 15, 2020 by Teachoo

Ex 13.5, 7 In an examination, 20 questions of true-false type are asked. Suppose a student tosses a fair coin to determine his answer to each question. If the coin falls heads, he answers 'true'; if it falls tails, he answers 'false'. Find the probability that he answers at least 12 questions correctly.Let X : be the number of questions he answers correctly Tossing a coin is a Bernoulli trial So, X has binomial distribution P(X = x) = nCx π^(πβπ) π^π Here, n = number of questions = 20 p = Probability of getting answer correct Since it is a true false question P(he answers correctly) = p = 1/2 Thus, q = 1 β p = 1 β 1/2 = 1/2 Hence, P(X = x) = 20Cx (1/2)^π₯ (1/2)^(20βπ₯) P(X = x) = 20Cx (1/2)^(20 β π₯ + π₯) P(X = x) = 20Cx (π/π)^ππ We need to find probability that he answers at least 12 questions correctly i.e. P(X β₯ 12) P(X β₯ 12) = P(12) + P(13) + P(14) + β¦β¦ β¦.. +P(20) = 20C12 (1/2)^20 + 20C13 (1/2)^20+ 20C14 (1/2)^20+ β¦β¦ + 20C20 (1/2)^20 = (π/π)^ππ(20C12 + 20C13 + 20C14 + β¦β¦.. + 20C20)