The teacher asked, "If a shepherd puts twenty sheep out to graze in a field, and five of them jump over a fence, how many sheep would be left?"
"None," called out little Mac.
The teacher said, "I'm surprised you can't count correctly. I know you're good at arithmetic, but you've made a mistake."
Little Mac replied, "You know arithmetic, teacher, but you don't know sheep. I know that if one sheep jumps, the rest will follow."