here:
http://www.gofuckyourself.com/showth...pagen umber=1
in short, there are 3 curtains. there's a car behind one of them (you don't know which one), and the 2 others are empty.
You chose one..
the host of the show reveals an empty curtain (there must be at least one left, or even 2 if you chose the one with the car behind it), and offers you to switch to the one left.
if you switch, what chance would you have to win?