Abacus Lesson 27: Subtractions using complements of 10, 100's column

Video Abacus Lesson 27: Subtractions using complements of 10, 100's column (Click Read more, then click video link

423 - 299 (423 minus 299)
Start from left to right
In the 100's column, take away 2
In the 10's column, complement if 9 is 1, add 1 in 10's column, take away 1 in 100's column
In the 1's column, complement of 9 is 1, add 1 in the 1's column, take away 1 in the 10's column
Answer is 124

861 - 187 (861 take away 187)
In the 100's column, take away 1
In the 10's column, complement of 8 is 2, add 2 in the 10's column, take away 1 in 100's column
In the 1's column complement of 7 is 3, add 3 in the 1's column, take away 1 in the 10's column
Answer is 674

384 - 185 (384 minus 185)
In the 100's column, take away 1
In the 10's column, complement of 8 is 2, add 2 in 10's column, not enough beads, complement of 2 is 3, take away 3 in 10's column, take away 1 in 100's column
In the 1's column, complement of 7 is 3, add 3 in 1's column, take away 1 in 10's column
Answer is 167

469 - 281
In 100's column, take away 2
In 10's column, complement of 8 is 2, add 2 in 10's column, take away 1 in 100's column
In 1's column, take away 1
Answer is 188

Now do Worksheet 27:

Video: Abacus Abacus Lesson 27: Subtractions using complements of 10, 100's column

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