QED

Op de website van Eric Postpischil, die bij Apple werkt als Senior Vector and Numerics Engineer, vond ik de volgende grap:

A physicist, a biologist, and a mathematician are sitting in a café and notice people going into and coming out of the house across the street. First they see two people going into the house. Time passes. After a while, they notice three persons coming out of the house.
The physicist: “The measurement was not accurate.”
The biologist: “They have reproduced.”
The mathematician: “If one person enters the house, then it will be empty again.”

Postpischil heeft nog een aantal andere leuke wiskundige grappen.