# Ex 13.5, 14 - Chapter 13 Class 12 Probability

Last updated at Dec. 8, 2016 by Teachoo

Last updated at Dec. 8, 2016 by Teachoo

Transcript

Ex 13.5, 14 In a box containing 100 bulbs, 10 are defective. The probability that out of a sample of 5 bulbs, none is defective is (A) 10–1 (B) 125 (C) 9105 (D) 910 Let X : be the number of defective bulbs Picking bulbs is a Bernoulli trial So, X has binomial distribution P(X = x) = nCx 𝒒𝒏−𝒙 𝒑𝒙 n = number of times we pick a bulb = 5 p = Probability of getting defective bulb = 10100 = 110 q = 1 – p = 1 – 110 = 910 Hence, P(X = x) = 5Cx 𝟏𝟏𝟎𝒙 𝟗𝟏𝟎𝟒−𝒙 We need to find Probability that no bulb is defective i.e. P(X = 0) P(X = 0) = 5C0 1100 9105 −0 = 1 × 1 × 9105 = 9105 Option C is the correct answer

Chapter 13 Class 12 Probability

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