File:Abacus-Whole-Numbers.png|Using an abacus to count whole numbers up to 1,000,000. The abacus shows the number as a sum of the units: ones, tens, hundreds, etc.
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File:Abacus-Whole-Numbers.png|Using an abacus to count whole numbers up to 1,000,000. The abacus shows the number as a sum of the units: ones, tens, hundreds, etc. [http://activities.sugarlabs.org/en-US/sugar/addon/4293]