Written by July 22, 2025
Abacus Math Program – Lesson 7 – Ten Pair Complement Subtraction Part 1
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In Lesson 5 and Lesson 6 we introduced the idea of 10 pair complement addition on the abacus. Here in Lesson 7 we will introduce the concept of subtraction with 10 pair complements. In review, there are only 5 possible 10 pair complements: 9-1, 8-2, 7-3, 6-4, 5-5. In the case where we want to subtract a number from a