3 girls in a hotel room order room service pizza. The room service boy brings the pizza, and it costs $30.00 Each girl gives $10.00 3x10=$30.00 The room service boy takes the money to the cashier. Cashier say it was a mistake, and the bill is only $25.00. Cashier gives back 5 $1 dollar bills to the room service boy to take back to the girls. $30.00 - $25.00 = $5.00 Going back to the room the room service boy decide to keep $2.00 for himself because he did not get a tip. That leave $3.00 to give to 3 girls in the room. So he does that. But if each girl gave $10.00, then got back $1.00 each from the room service boy, that means each girl paid $9.00 for the pizza bill. If $9.00 x 3 = $27.00 and the room service boy kept $2.00 for the tip... $27.00 + $2.00 = $29.00 what happened to the other $1.00? Remember the bill was $30.00.