Three guys go into a motel, the clerk says that will be 30usd.
Each guy pays 10.
Later the manager comes in and says it should have been 25 and to give them a refund.
The clerk decides since 5 doesn't divide evenly by 3 that he would keep 2 and give each fella back 1 dollar.
So, each fella paid 9 dollars.
3 times 9 is 27.
27 plus the 2 in the clerk's pocket makes for 29usd.
Where is the other dollar?