The all possible eight outcomes of boy or girl birth when a couple have three children is
(GBB) , (GBG), (GGB) , (GGG), (BBG), (BGB), (BGG), (BBB)
Where B represents boy and G represents Girl
The probability that having exactly 1 girl is
= Number of outcomes with one girl / Total numbers of outcomes
Now Number of outcomes with only one girl = GBB, BGB, BBG = 3
So the probability will be
The probability that having exactly 1 girl is = 3/8 = 0.375
The probability that when a couple has three children, there is exactly 1 girl is 0.375
