A baby is added to a hospital nursery. Before the baby was added there were two boys in the nursery and an uncounted number of girls. After the new baby is added a baby is selected at random among all the babies. The selected baby is a boy.

What is the probability that the added baby was a girl?

I'm guessing 50%, because nothing in problem effects the liklihood/sex of the baby added. Kind of like, if you flip a coin 3 times, and it turns up heads, what's the probability that the 4th flip will also be heads -> 50%.

Posted by e on 2003-10-09 19:00:47