Question 435571: A family has three children. What is the probability that the first is a boy given that one is a girl? Answer by robertb(5830) (Show Source):
You can put this solution on YOUR website! The following list gives the sample space (assuming no multiple births!)
BBB
BBG
BGB
BGG
GBB
GBG
GGB
GGG
There are 7 sample points where there is at least 1 girl. Of these seven , there are 3 elements where the first child is a boy. Hence the probability that the first is a boy given that one is a girl is 3/7.
