Abacus

An abacus is a tool that you can use to do math. It looks like a rectangular frame with a bunch of beads on it. Each row of beads has a different value. The bottom row is worth one, the row above it is worth ten, and so on. To use it, you move the beads to add or subtract, just like counting on your fingers. It makes it easier for people to do math problems quickly, without using a calculator.