Joke - Where is the other $1?

Three guys get a hotel room for $10 each. Realizing that he had charged too much, the clerk sent the bellman to the room with $5. The bellman put $2 in his pocket and gave each guy back $1. Now each guy has paid $9 for the room. $9 X 3 = $27 + $2 = $29 Where is the other $1?