There was a guy who wanted to know how to calculate the volume of a red rubber ball.
He took the ball to a mathematician, who measured its radius and used the formula, V = 4/3*π*r3, to find its volume.
Next, he took the ball to a physicist, who submerged the ball in a bowl of water and calculated the volume of the ball by the amount of water that was displaced.
Still not satisfied, he took the ball to a mechanical engineer. The engineer says, “Hold on a second, I got this.” He gets up and rummages through the books on his shelf. “Ah, this should do it,” he says and pulls out a big, fat, hard-bound book titled, “Mechanical Engineers’ Handbook for Red Rubber Balls.”