Three friends went to a motel after a long night of driving. They they didn't have much money so they decide to split the bill and just get one room for the night. The motel manager said a room cost $30, so each man put up $10 and went to their room. A little while later the manager realized the room was only $25, so he sent the bellhop back to the three guys' room with $5. They were happy to get back some change so they gave the bellhop a $2 tip and split the other three each taking $1.
This meant that the 3 men paid $9 each for the room for a total of $27. Add the $2 that the bellhop kept = $29.
Where did the other dollar go? Don't ruin the fun by blurting out the answer.