3 guys are going on a hunting trip and each pitch in $10 on a hotel room. They pay the desk clerk, get the key and go to the room to get some sleep for an early morning adventure. The clerk's boss shows up and tells the clerk he had promised the room to the hunters for $25. He gives the clerk $5 in one dollar bills and tells him to take it to the hunter's room and refund them the $5. The hunters are so happy with the honesty of the hotel, they each accept a $1 bill and tip the clerk $2 for his trouble.
So each hunter has now paid $9 a piece for their room for a total of $27. Add that back to the $2 the clerk got for a tip and you only come up with $29. What happened to the missing $1?