Jim, Jon and Joe all enter a cheap motel looking for room for the night.
They walk to the front desk and ask, "How much is a room here for one
night?".  

"I am not sure, I think it is $30.  Just one room?"

"Yep."  Jim, Jon and Joe all pay $10 each and go off to their room.

Later the manager of the cheap motel returns and the front desk man asks,
"How much was I supposed to charge for one room with three guys in it?"

"$25.  Now you had better go and give them back their $5!"

The front deskman got five one dollar bills and starting walking over to
the motel room.  He was wondering how to break up five dollars between
three men, when he came up with a "brilliant" solution.  Why not give them
each one dollar and pocket the other two dollars.  

"Hi, I overcharged each of you one dollar."  He gave each of them one
dollar and left with his two dollars.

The real mystery lies here.  Each of the guests paid $10 dollars and then
recieved back $1.  So each paid a total of $9.  Three guests times $9 is
$27.  Add to that the $2 the front deskman pocketed and you get $29.  They
originally paid $30.  Where did the other $1 go?