My favorite math joke.

A mathematician and a physicist were asked the following question:

Suppose you walked by a burning house and saw a hydrant and a hose not connected to the hydrant. What would you do?

P: I would attach the hose to the hydrant, turn on the water, and put out the fire.
M: I would attach the hose to the hydrant, turn on the water, and put out the fire.

Then they were asked this question:

Suppose you walked by a house and saw a hose connected to a hydrant.

What would you do?

P: I would keep walking, as there is no problem to solve.
M: I would disconnect the hose from the hydrant and set the house on fire, reducing the problem to a previously solved form.

There are many versions of this joke this one came was found at, http://cnonline.net/~TheCookieJar/math_jokes_02.html

Lets start with a joke.

One day a farmer called up an engineer, a physicist, and a mathematician and asked them to fence of the largest possible area with the least amount of fence. The engineer made the fence in a circle and proclaimed that he had the most efficient design. The physicist made a long, straight line and proclaimed "We can assume the length is infinite..." and pointed out that fencing off half of the Earth was certainly a more efficient way to do it. The Mathematician just laughed at them. He built a tiny fence around himself and said "I declare myself to be on the outside."