A man goes into a store and selects four items to purchase. He walks up to the counter to pay and the clerk says “Hold on, my cash register is broken, so I have to use a calculator to get your total… okay, that’ll be $7.11” The man pays, and as he is walking out, the clerk yells “Wait a second! I multiplied the prices together instead of adding them. Let me get the total again… hey, what do you know! It comes out the same!”
What were the prices of the four items? All of them are of the form a.bc, that is, we’re dealing with standard U.S. money, no fractions of a cent. Ignore sales taxes too.