three men go into a hotel. they are charged $30 for the night.  Each
man pays $10 dollars.  the manger decides he has over charged them and
tells his son to give the men back $5.  The boy cannot divide $5 three
ways so gives each man $1 and pockets the remaining $2.   So
3 men each pay $9 = $27 plus the $2 the boy pocketed, equals $29.
Where is the remailing $1

I'm no math guru, but the following query: where $1 $30 men hotel

led me to http://hive-mind.com/mindgames/hotel/

Solution is located there as well.

This is a trick question designed to confuse. Each man paid nine
dollars for a total of $27. $25 went to the manager and $2 to his son.
There isn't any reason the $27 plus $2 should add up to what the men
originally paid.

This is an ancient brain-teaser. I first came across it when I was a
child in the 1950s. You can tell that it is old: is there any hotel
anywhere today with room rates like that? ;-)