Three men check into a hotel. They pay $30 the hotel manager and go to their room.
The manager suddenly remembers that the room rate is $25 and gives $5 to the bellboy to return to the men.
On the way to the room the bellboy reasons that $5 would be difficult to share among three men so he pockets $2 and gives $1 to each man.
Now each men paid $10 and got back $1. So they paid $9 each, which costs them in total $27.
The bellboy has $2, totalling $29.
Where is the missing $1?