If There Are 20 People In A Room, There’s A 50/50 Chance That Two Of Them Will Have The Same Birthday.

Before you read the answer, see if you can figure out the correct answer. How is this possible?

 

This phenomenon actually has a name -- it is called the birthday paradox, and it turns out it is useful in several different areas (for example, cryptography and hashing algorithms).

You can try it yourself -- the next time you are at a gathering of 20 or 30 people, ask everyone for their birth date. It is likely that two people in the group will have the same birthday. It always surprises people!

via HowStuffWorks "Someone told me that if there are 20 people in a room, there's a 50/50 chance that two of them will have the same birthday. How can that be?".