Three people check into a motel. They pay $30 to the desk clerk and go to their room. The desk clerk finds out that the room rate is $25 and gives $5 to the bellhop to return. On the way to the room the bellhop reasons that $5 would be difficult to share among three people so he pockets $2 and gives $1 to each person.
Now each person paid $10 and got back $1. So they paid $9 each, totalling $27. The bellhop has $2, totalling $29.
Where is the remaining dollar?