Three men traveling, stop at a hotel for the night. They opt to share a 3 bed room. The room cost $30.00. Each man pays the deskclerk $10 and leave for their room.
The deskclerk realizes he overcharged the men by $5 and gives the change to the porter to return to the guest. The porter realizing that the $5 won't split evenly between 3 people, keeps $2 and gives each man $1.
each man has paid $9 for the room, that's $27 dollars paid by the three men, and $2 in the porters pocket. 27+2 = 29.
Where did the last dollar go?
Now the real riddle here I believe is, where on earth do you get a room for $30 One that you would want to stay in anyway.