Written by January 13, 2026
Build Calculation Speed Practicing the 10 Pair Complements
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The main method of addition and subtraction on the abacus is understanding and using the 5 complement pairs of 10, i.e. pairs of numbers that add to 10. There are only 5 complement pairs in our base 10 numbering system: 9 and 1, 8 and 2, 7 and 3, 6 and 4, and 5 and 5. The faster