There are three men that each are on a business trip and decide that it would be cheaper to share a hotel room and split the cost.
The room was $30 so they each paid the lobbyist $10 and then went up to their room.
The bus boy brought their bags up, handed them $5 back, and said that their room was on special tonight for $25, and the lobbyist forgot.
The three men decided that the easiest way to split up the $5 between the three was to take a $1 back each and give the extra $2 to the bus boy for a tip. This means that each person paid $9 each and with the three of them, that makes $27.
Then if you add the two dollars for the bus boy's tip that should make $29.
What happened to the extra dollar?
Hint: get out some play money and role-play the situation.
Solution Commentary: Build columns...what each man paid, who got what (e.g. bus boy, clerk). Discover how the problem is sleight-of-hand in the sense that its narration causes you to focus on something that basically does not exist.