James and Calie are a married couple.

They have two children, one of the child is a boy. Assume that the probability of each gender is 1/2.

What is the probability that the other child is also a boy?

**Answer :** 1/3

**Solution :**

This is a famous question in understanding conditional probability, which simply means that given some information you might be able to get a better estimate.

The following are possible combinations of two children that form a sample space in any earthly family:

Boy – Girl

Girl – Boy

Boy – Boy

Girl – Girl

Since we know one of the children is a boy, we will drop the girl-girl possibility from the sample space.

This leaves only three possibilities, one of which is two boys. Hence the probability is 1/3.