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Abacus

 
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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.

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 abacus can also be used to carry out multiplications, divisions, and even the calculation of roots.

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.