Slide rule

A slide rule is a tool that was used before calculators to do math calculations quickly. It looks like a ruler, or measuring stick, but it has special markings on it that can be used to help solve math problems. You can use it to add and subtract, multiply and divide, and figure out roots and squares. To do this, you slide one part of the ruler (called the "cursor") against the other part of the ruler (called the "body" or the "stock") until the numbers line up correctly. Then, you read the answer off where the two parts of the ruler were lined up. Slide rules were used by people like engineers and scientists to do math quickly and accurately.