**

*🌎*

*▾*

**

*🔑*

**

This animation represents the Japanese abacus (*soroban*). Balls are strung along rods (columns). Each rod corresponds, going from right to left, to ones, tens, hundreds, thousands…

The upper balls have a value of 5. The lower ones have a value of 1. In other words, an upper ball on the third rod from the right has a value of 5 hundreds (500).

A lower ball on the second rod from the right has a value of ten (10).

A ball is only counted when it has been moved down to the transverse (horizontal) bar.

**Click **on a ball in order to slide it.

**Click **on the "labels" button (three horizontal lines inside a circle) on the navigation bar to show or hide the values.

- To illustrate the principles of the base ten system.
- To illustrate the rule of complements of 5 and 10.
- To visualize carrying over.

The principle of the **abacus **has been known since the 3rd millenium BCE (the Mesopotamians). It enables one to carry out simple operations like additions and subtractions, but, in expert hands, the…