To add a + b, start at a on the plus scale. Then move b units. You’ll end up at a + b.
To multiply a × b, connect 1 on the plus scale with a on the times scale. Then, draw a parallel line that goes through b on the plus scale. It will go through a × b on the times scale.To extract √a, draw a semicircle from the “tail” 1, to a on the plus scale. It will go through √a on the square-root scale.
Geeks out of the box 