Monday, March 31, 2014

2014/031) A question on probability

I was walking through the park when I bumped into an old acquaintance.

He told me that he had two children. What is the probability that he has two girls?

A girl joined us. He said it was one of his children. What is the probability that he has two girls?

He said she was his eldest child. What is the probability that he has two girls?

Answer
probability that both are girls = 1/2 & 1/2 = 1/4

given that one is a girl it does not matter whether elder or younger probability that both are girls = probability that 2nd one girl = 1/2

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