18.01.2013, 17:17
Actually, there's no lost dollar: it's the thing that is thought the wrong way just to confuse people. The 3 boys DO NOT have paid $27 in the end! The seller got $25 in the end, the boys $3 and the boy $2. It's like they paid $30, but got back $5, and gave again $2 to the boy, so it's like they gave $28 overall.