How do you use a slide rule?

Answer 1

the slide rule, also known colloquially as a slipstick,is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for "scientific" functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.

Slide rules come in a diverse range of styles and generally appear in a linear or circular form with a standardized set of markings (scales) essential to performing mathematical computations. Slide rules manufactured for specialized fields such as aviation orfinance typically feature additional scales that aid in calculations common to that field.

To give a sample of how the slide rule works, here are two simplified descriptions of how two numbers are multiplied on a slide rule using the A and B scales:

Multiplying 2x3: The line at the left end of the B scale, associated with the number 1, is placed at the first of the numbers being multiplied, 2, on the A scale, by moving the slide. We look up from the second number being multiplied on the B scale, 3, and find the number above it on the A scale is 6. When the result is to the left of the 1 in the middle of the A scale, the number of decimal places in the result is the sum of the number of decimal places in the multipliers, minus one. So in this case, the number of decimal places is 1.

Multiplying 3x4: The line at the left end of the B scale, associated with the number 1, is placed at the first of the numbers being multiplied, 3, on the A scale, by moving the slide. We look up from the second number being multiplied on the B scale, 4, and find the number above it on the A scale is 12. When the result is to the right of the 1 in the middle of the A scale, the number of decimal places in the result is the sum of the number of decimal places in the multipliers. So in this case, the number of decimal places is 2.

This might sound really complicated, but once you get the hang of it, it is easy. Unfortunately, it is not like riding a bike. Once you have learned, it is really easy to forget anyway.