A calculator won't help at all if you don't have a grasp on what compound interest is. I've seen many laments on X from graduates who could not understand why they've paid more money to their student loan lender than the amount of the loan, and still have a balance that was more than the loan amount.

These are college graduates.

> Does a solid knowledge of, e,g, Set Theory, give any benefit later in life?

Knowledge of statistics will help a person a lot.

Another example. I wanted to put an elliptical brick patio in my yard. The contractor gave a square footage and I signed a deal with the charge per square foot. He staked it out.

It looked a bit peculiar to me. So I measured the major and minor axes and computed the area of the ellipse. It was 1/3 smaller than the contracted amount. The pallet of bricks was sitting in the driveway. I multiplied xyz to get the square footage of the bricks, and walla, it matched the area staked out.

I.e. I was being cheated. The contractor evidently was used to math challenged customers, and discovered how much he could cheat before being noticed. I pointed out the "error" (hahahaha) and the contractor reduced the bill by a third.

> why don't we teach that?

Exactly!