CSflim

I said #1, because I may even post another! Wow! Imagine that!

Anyway, I would ask that you post your answer before reading the other replies!

So anyway, here it is:

I pass by a window, and peer in. I see a group of people inside. I conclude that there is (approximately) a 50% chance that two of those people share a birthday. How many people are in the room?

Its not a trick question BTW. There isn't a banner hanging up inside that says "Happy Birthday John and Mary" or a pair of identical twins or anything like that! It's as straight forward as it looks!

__________________