Monte Hall Problem
(3 doors)There are 3 closed doors in front of you. One of them has a pile of money behind it, and the other two have stinking pigs. You want to win the money, of course. You pick a door. One of the other two doors has a pig behind it of course, and so one of the other two doors is opened showing the pig. Now you have another chance to pick, and either stay with the original choice or switch. What is the better strategy to win?
.. Lots of other visual math tutorials at shodor.org