Little Johnny is always being teased by the neighborhood toughs for being stupid. Their favorite joke is to offer Johnny his choice between a nickel and a dime. Little Johnny always takes the nickel, causing no amount of snickering and glee among the bullies.
One day, after Johnny takes the nickel, nice Mr. Johnson pulls him aside and says, "Johnny, those boys are making fun of you. Don't you know that a dime is worth more than a nickel, even though the nickel is bigger?"
Johnny grins and says, "Well, if I took the dime, they'd probably stop. Right now I'm up more than twenty bucks on those mooks!"