# Slide Rule

Lately I have been learning how to use two traditional calculation tools, (1) the Soroban, a.k.a., Abacus, and (2) the slide rule. My co-worker lent me his Pickett Model N-16-ES ELECTRONIC slide rule:

"ELECTRONIC" means it was made for electronics applications, I'm told.

The slide rule is based on the concept that the multiplication of two numbers is equal to the addition of their logarithms. So, the numbers are printed on the rulers in their logarithmic positions and then the scales are added together.

Multiplication and division are fairly simple and quick, but due to the limitations of the marks on the rulers and human eyesight, you are limited to 3 significant digits. In many applications, however, 3 significant digits is plenty, so long as you can keep track of the exponents that need to be multiplied back in (e.g., 1.45e3 x 5.67e4 means you need multiply back in 10^7).

I was curious if one could perhaps multiply faster using a slide rule rather than a hand calculator, since you have two or three sliding actions rather than many key presses. However, if you were fair you need to limit the calculator calculation to 3 significant digits also, in which case using the calculator is pretty fast. I don't see how you would be able to win out over the calculator no matter how much you practiced.

Nonetheless, the slide rule seems like a good tool to have along if you want something available that does not depend on electricity.

Here is great explanation of how to do the operations:

Illustrated Self-Guided Course On How To Use The Slide Rule

## Comments

### Alaskalinuxuser, 2021-08-22

I have now spent way too much of my weekend trying to figure out how a slide ruler works. :)