Friday, December 20, 2013

Idiot Math

I'm bad at math. So I do what I think of as "idiot math", which I do really well, frequently leaving people with the mistaken impression that I'm good at math. I'm not good at math, I'm just good at doing idiot math.*

The other day I needed to buy eight 46 cent shelf brackets at the hardware store. As the guy was trying to find his calculator, I doubled 46 to get 92, and doubled that to get 1.84, and doubled that to get 3.68. Voila.

If I need to multiply 197 x 9, I multiply 200 x 9 instead, just 'cuz it's easier. So that's 1800, and I need to make up for my laziness by subtracting the missing 3 x 9 (or 27) to get 1773. If I'm feeling too bleary to subtract 27 from 1800, I subtract 30 instead, to get 1770, and then add back the missing 3 to get 1773. I just take the easiest nearby calculation, then compensate for the overage/underage, and it can go back and forth in a cascade of simple-minded calculation and diligent compensation.

I know, it reads super complicated, but the point is that no one calculation is at all difficult. If you keep the calculations easy, then it's possible to focus on the big picture - of exactly how much you're miscalculating - so you can compensate. Let go of the calculations, in other words, and direct attention toward the overarching logic.

* it's not paradoxical to say you're good at doing things poorly. I have the same situation with Spanish, where I don't have a great vocabulary, but am very fast and agile at applying the wrong words. For example, I may not know how to say "drapes", but can very fluently rattle off "the cloth things which cover windows so light doesn't come in").


JB said...

I'm good at math, mostly by using your idiot math!

Jim Leff said...

No, if you're good at math, you do the direct calculation. Math's all about calculation, and if you're good at that, there's no need to resort to this much more complex system of fudging and compensating.

What you're good at is logic, which is a whole different faculty!

Blog Archive