The Missing Dollar
Three
men go into a hotel to share a room for the night. The hotel clerk tells them the room is $30 for the night, so each man hands over a $10 bill and they go upstairs. A few minutes later the clerk realizes he made a mistake, and that the room is only $25 for the night, so he hands the bell-hop five single dollar bills to go refund the three men in their room. On the way up the bell-hop realizes that he cannot evenly distribute five singles amongst three men, so, deciding that the guests are none the wiser, he pockets $2 and gives each man back $1.
So, the guests originally each paid with a $10 bill, and received back a dollar each, for net spending of $9 each. The bell-hop has $2 in his pocket. $9 times each of the three guests is $27, plus the $2 in the bell-hop's pocket equals $29, but they originally spent $30. Where's the missing dollar?