Maybe this has already been posted. A friend asked me this a while back, and I answered her in less than a minute.
She said I was a genius. But I said there were two ways to arrive at the answer, and I simply chose the easier way.
A 6-inch [long] hole is drilled through [the center of] a sphere.
What is the volume of the remaining portion of the sphere?
The hard way involves calculus. The easy way uses logic.