The funny (?) thing about my answer is that my Mom was musing (when I was young) about why manhole covers are round, and I gave the explanation that I gave you - and then I had to act it out for her with a piece of cardboard or something, because Mom is sphere inept in geometry for reasons that neither she nor I have ever been able to explain. She can work the problems on paper just fine, but the underlying intuitive grasp of it is not there.

She said I was very smart.

I looked at her perplexed, because I couldn't understand how it wasn't obvious to her.