Little Johnny is always being teased by the other neighborhood boys for being stupid. Their favorite trick is to offer Johnny his choice between a nickel and a dime. Little Johnny always takes the nickel.
One day, after Johnny takes the nickel, a neighbor takes him aside and says, "Johnny, those boys are making fun of you. Don't you know that a dime is worth more than the nickel, even though the nickel's bigger?"
Johnny answers, "Well if I took the dime, they'd stop doing it, and so far I've made $20!"