The Missing Dollar
See what your class thinks of this problem:
Three men went to a motel. The man behind the desk said the room is $30, so each man put up $10 and went to the room. A little while later the man behind the desk realized the room was only $25, so he sent the bellboy back to the 3 guys' room with $5. On the way to the room the bellboy couldn't figure out how to split the $5 between the 3 men, so he just gave each one of them $1 and he kept the other $2. This meant that the 3 men paid $9 each for the room for a total of $27. Add the $2 that the bellboy kept = $29. Where's the other dollar?