Abacus Lesson 30: Addition, Compound Complements of 10, 100's column

267 + 165
Add 1 in the 100's column
Complement of 6 is 4, complement of 4 w.r.t. 5 is 1
Add 1, take away 5, add 1 in next column (carry 1)
Complement of 5 is 5, take away 5, add 1 in next column (carry 1)
Answer is 432


851 + 69
Complement of 6 is 4, complement of 4 w.r.t. 5 is 1
Add 1, take away 5, add 1 next column (carry over)
Complement of 9 is 1, take away 1, add 1 in next column (carry 1 over to next column)
Answer is 920

777 + 166
Add 1 in 100's column
Compound complement of 6, add 1, take away 5, carry 1
Repeat in 1's column
Answer is 943

173 + 572
Add 5 in 100's column
Complement of 7 is 3, complement of 3 w.r.t. 5 is 2
Add 2 in 10's column, take away 5, add 1 next column
Answer is 745

481 + 262
Complement of 2 is 3, take away 3, add 5
Complement of 6 is 4, complement of 4 w.r.t. 5 is 1
Add 1 in 10's column, take away 5, add 1 in 100's column
Add 2 in the 1's column
Answer is 743

258 + 585
Add 5 in 100's column
Complement of 8 is 2, compound complement of 2 is 3
Add 3 take away 5 in 10's column, carry 1 over
Complement of 5 is 5, take away 5, carry 1 over
Answer is 843

Now do the worksheets

Answer is 743

Video: Abacus Lesson 30: Addition, Compound Complements of 10, 100's column

Acknowledgement: The above is a summary of HEV Project video lessons.