# Ex 13.5, 13 - Chapter 13 Class 12 Probability

Last updated at Dec. 18, 2018 by Teachoo

Last updated at Dec. 18, 2018 by Teachoo

Transcript

Ex 13.5, 13 It is known that 10% of certain articles manufactured are defective. What is the probability that in a random sample of 12 such articles, 9 are defective? In each of the following, choose the correct answer: Let X : be the number of defective articles Picking articles is a Bernoulli trial So, X has binomial distribution P(X = x) = nCx n = number of articles = 12 p = Probability of getting defective articles = 10% = 10 100 = 1 10 q = 1 p = 1 1 10 = 9 10 Hence, P(X = x) = 12Cx (๐/๐๐)^๐ (๐/๐๐)^(๐๐โ๐) We need to find Probability of getting 9 defective articles out of 12 i.e. P(X = 9) P(X = 9) = 12C9 (1/10)^9 (9/10)^(12 โ 9) = (12 !)/((12 โ 9) ! 9 !) (1/10)^9 (9/10)^3 = (12 ร 11 ร 10 ร 9 !)/(3 ! 9 !) \ ร1/ใ10ใ^9 (9/10)^3 = (12 ร 11 ร 10)/(3 ร 2 ร 1) ร 1/ใ10ใ^9 (9/10)^3= (2 ร 11)/ใ10ใ^8 9^3/ใ10ใ^3 = 22 (๐^๐/ใ๐๐ใ^๐๐ )

Chapter 13 Class 12 Probability

Serial order wise

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