[lcruzrlvr]

Three women are eating lunch together and the bill comes to $30.
Each woman hands the waiter a $10 bill for her portion.

The waiter takes the money to the register and realizes he should have only charged them $25. He takes 5 - $1 bills out of the register and starts walking back to the table.

He knows he is going to be asked to make even change so he simply pockets 2 of the $1 bills. (More honest than just skipping with the entire $5 in change.)

He then hands each woman 1 - $1 bill. Each woman's portion of the meal was now $10 minus $1 equaling $9 or $27 total. He has 2 - $1 bills in his pocket. $27 plus $2 = $29.

Question: Where did the other $1 go?

This is why I8math.