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A man visits a couple who have 2 children. one of the children, a boy, comes into the room.

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A man visits a couple who have 2 children. one of the children, a boy, comes into the room. find the probability p that the other is also a boy.

(a)1/3

(b)2/3

(c)1/2

(d)3/4

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Since, it's given that the first one is a boy, the second event is independent of the first and the probability is 1/2.(The sample space contains only the events concerning the second child ({G, B}) . Had the question been "what's the probability of both the children coming to the room being boys given that one is surely a boy", then the sample space will contain BB, BG and GB and probability would be 1/3)

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