Here’s a puzzle for you. A group of three men go to a hotel, and they each pay $10 for a room, for a total of $30. Afterwards, the manager remembers that there’s a deal where you can get 3 rooms for $25, so he gives $5 to the bellboy and tells the bellboy to return it to the men. But the bellboy returns just $1 to each of the men, and pockets the remaining $2.
So the men each paid $9, for a total of $27. The bellboy pocketed $2. Where did the other dollar go?