Abacus Lesson 28: Addition, Compound Complements of 10, 1's column

6 + 7
Complement of 7 is 3, complement of 3 w.r.t. 5 is 2
Add 2, take away 5, add 10
Answer is 13

5 + 6
Complement of 6 is 4, complement 4 w.r.t. 5 is 1,
Add 1, take away 5, add 10
Answer is 11

7 + 7
Complement of 7 is 3, complement of 3 w.r.t. 5 is 2
Add 2, take away 5, add 10
Answer is 14

6 + 6
Complement of 6 is 4, complement of 4 w.r.t. 5 is 1
Take away 5, add 1 add 10
Answer is 12

5 + 8
Complement of 8 is 2, complement of 2 w.r.t. 5 is 3
Add 3, take away 5, add 10
Answer is 13

8 + 6
Complement of 6 is 4, complement of 4 w.r.t. 5 is 1
Take away 5, add 1, add 10
Answer is 14

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Acknowledgement: Credit to John of HEV Project for the abacus lesson videos and worksheet