Slide Rulers - Explained

Slide rules are simple... imagine 2 rulers.... if you move the end of one to a given position on another.... you can add / subtract with them.

A slide ruler uses a special scale that does the same job, except when you're done... you get the product of the numbers, instead of the sum. If you run it backward, you get division.

The only other real trick is that they wrap back around to 1 at the ends to make it easier mark (less numbers) and let you use them for any size numbers.

Fancy ones have scales that are 1/2 and 1/3 the space between marks to let you square and cube in one operation, and also add trig and log-log scales, etc.