"Everybody LOVES a math joke"

Judging by the facebook group "I Wish I Were Your Derivative So I Could Lie Tangent To Your Curves!" with 42,000 members, everybody loves a math joke. My roommate, a math major, is especially into them...here's one she loves to tell (copied from an article in the American Mathematical Society Journal, with a link to the article below). Seriously, she even told it at a Harvard party that we went to, with an audience of future lawyers and chemists:

"A biologist, a physicist, and a mathematician were sitting in a street café watching the crowd. Across the street they saw a man and a woman entering a building. Ten minutes later they reappeared together with a third person. “They have multiplied,” said the biologist. “Oh no, an error in measurement,” the physicist sighed. “If exactly one person enters the building now, it will be empty again,” the mathematician concluded."

If you're interested, check out this article in the American Mathematical Society Journal, called Foolproof: A Sampling

of Mathematical Folk Humor by Paul Renteln and Alan Dundes

Here are some I received in an email:

I've definitely felt like doing this before....