My Favorite Math Joke!

A farmer has 100 ft of fencing and wants to enclose as large an area as possible, so he does the obvious thing, and hires an engineer, a physicist, and a mathematician to consult him. The engineer quickly pens in a square with the 100 ft and says voila! The physicist, knowing he can optimize this, goes to the blackboard and finds that a circle would enclose a larger area. The mathematician, after much deep thought, pulls out two feet of fencing, wraps it around his waist, and yells "I declare myself to be on the outside"!