There are two houses. The first house has a boy and another child. In the second house, there is a 10-year-old boy and an infant. Which place has a girl?
Well, it is impossible to predict the house with a girl with 100% certainty. But one of the houses has a higher probability of having a girl than the other.
The first house can have three possible combinations – (boy, boy), (boy, girl) and (girl, boy). So finding one girl in the combinations is 2/3. Since we know the first child is a boy in the second house, there are only two possible combinations – (boy, girl) or (boy, boy). So finding a girl in that house is 1/2.
So choosing house 1 gives a higher probability for a girl.
