A mathematician and a…eh…non-mathematician are sitting in an airport
hall waiting for their flight to go. The non has terrible flight panic.
“Hey, don’t worry, it’s just every 10000th flight that crashes.” “1:10000?
So much? Then it surely will be mine!” “Well, there is an easy way
out. Simply take the next plane. It’s much more probable that you go from a
crashing to a non-crashing plane than the other way round. So you are
already at 1:10000 squared.”