Three friends are out late one night and decide to get a hotel room instead of driving home. They get to the hotel and purchase a room for the night, the room is $30. The friends decide to split the room three ways, $10, $10 and $10.
Later in the night the cashier realizes he overcharged the friends and that the room was only $25 dollars and not the $30 he charged them. So, the cashier gives $5 to the bellhop and asks him to deliver it to the friends in the room. Realizing there wasn't a way to split the $5 three ways evenly, the bellhop decided that instead of giving the the whole $5 to the friends he could keep $2 and give the friends each $1 back.
With the friends each receiving their $1 back the ended up playing $9 each for the room..
So here's the riddle.. Each friend payed $9 for the room (originally paying $10 and receiving $1 back)
3 friends x $9 = $27
The bellhop kept $2
$27 + $2 the bellhop kept = $29
There was $30's out there, so where did the extra $1 go??