To the right are the outcomes that are possible when a couple has three children. assume that boys and girls are equally likely, so that the eight simple events are equally likely. find the probability that when a couple has three children, there is exactly 1 girl.

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