No longer updated!

Saturday, July 26, 2008

Boys and Girls

Ronald and Michelle have two children. The probability that the first child is a girl, is 50%. The probability that the second child is a girl, is also 50%. Ronald and Michelle tell you that they have a daughter.

The Question: What is the probability that their other child is also a girl?

A Hint 50% is not the correct answer.

Answer: There are four possibilities for two children:

The fourth possibility drops out, because Ronald and Michelle have a daughter. Therefore, three possibilities remain, of which in one case the other child is also a girl. So, the probability is 1/3 (about 33%).

No comments: