Lifted directly from "Math Jokes 4 Mathy Folks" blog:
A farmer was showing his fields to a mathematician and his wife. The mathematician made continual attempts to impress with his intellect, referencing arcane formulas and then doing computations mentally. Frustrated by this, the farmer decided to teach him a lesson. He took them to a field packed with hundreds of cows and said to the mathematician, “If you can guess the exact number of cows in this field, you can have all of them! But if you get it wrong, I get to sleep with your wife!”
The mathematician thought for a moment, his eyes quickly scanning the entire field. Finally he said, “228.”
The farmer was stunned. “How on Earth did you do that?” he asked. ”There’s no way you could have counted all those cows so quickly!”
“You’re right,” the mathematician replied. “‘I counted their legs and then divided by 4.”
And check out the rest of the latest "Carnival of Mathematics" HERE.