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seen May 5 '13 at 2:51

Dec
22
comment In a family with two children, what are the chances, if one of the children is a girl, that both children are girls?
sorry, re-reading your answer now I see that you have stated it correctly. Not sure if I read it wrong earlier or you have edited it. It is most certainly correct as stated.
Dec
21
comment In a family with two children, what are the chances, if one of the children is a girl, that both children are girls?
Your answer is correct for the OP's question, but not how YOU pose the question. Your text says "the first child is a...". That being said, if we know the first child is a girl, then out of bb, bg, gb, and gg, only gb, and gg are left available. Hence the probability is 1/2. Had you phrased it like the OP ("if we have a family with one girl (not necessarily the first child), what is the probability that both are girls?"), then your answer would be correct.