A biologist, a mathematician and a physicist are all watching an empty building.
They see a man and a women enter, later, two men and a women leave.
"Aha", says the biologist, "they've reproduced!"
"No," says the physicist, "our initial presumption must have been wrong."
"Well," says the mathematician, "if one more person enters the building, it'll be empty again."
An engineer, a mathematician and a physicist go hunting. The physicist spots a deer, measures the windspeed, weight of the bullet and explosive, punches the numbers into a calculator and takes the shot. He's off to the left by two feet.
"Well, no wonder you missed with a gun like that." The engineer pulls out a gun with a laser range-finder, wind compensation, automatic stabilizers, you name it. He shoots and is off the right by two feet.
They both turn to the mathematician, who just says "On average, we got it right between the eyes!"