Abacus Lesson 24: Addition, Complementary Numbers Respect to 100'S Column

Abacus Lesson 24: Addition - Complementary Numbers Respect to 100'S Column

364 + 107
Do from left to right, do the 100s column, then the 10s column, then the 1s column
In the 100s column add 1
In the 10s column, add nothing
In the 1s column, complement of 7 is 3
Take away 3 in the 1s column, add 1 in the 10s column
Answer is 471

875 + 15
Do from left to right, do the 10s column, then 1s column
In the 10s column add 1
In the 1s column, complement of 5 is 5, take away 5 in the 1s column, add 1 in the 10s column
Answer is 890

999 + 1
In the 1s column, not enough beads, complement of 1 is 9
In the 1s column, take away 9, in the 10s column add 1
In the 10s column, complement of 1 is 9, take away 9 in the 10s column, add 1 in the 100s column
In the 100s column, complement of 1 is 9, take away 9 in the 100s column, add 1 in the 1000s column
Answer is 1,000


255 + 55
In the 10s column, complement of 5 is 5, subtract 5 in 10s column, add 1 in 100s column
In the 1s column, complement of 5 is 5, subtract 5 in 1s column, add 1 in the 10s column
Answer is 310

27 + 388
In the 100s column, add 3
In the 10s column, complement of 8 is 2, take away 2 in 10s column, add 1 in 100s column
In the 1s column, complement of 8 is 2, take away 2 in the 1s column, add 1 in the 10s column
Answer is 415

611 + 199
In the 100s column, add 1
In the 10s column, complement of 9 is 1, subtract 1 in 10s column, add 1 in the 100s column
In the 1s column, complement of 9 is 1, subtract 1 in the 1s column add 1 in the 10s column
Answer is 810

Now do Worksheet 24

Video: Abacus Lesson 24: Addition - Complementary Numbers Respect to 100'S Column

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