I read this in a magazine yesterday (it's a story, it was about big mistakes):
Two people were working in a house, and one had to go get 50 meters of electric wire. So he went to a hardware store, and bought 50 meters of wire. When he got back he didn't realise what he did wrong, everyone was laughing, and he was still wondering why the people at the hardware store were laughing too.
He measured one meter, and cut off a piece... 50 times.