Solution to

To check an addition problem, simply reverse the order of the addends

Frame 1-26

and add again. For example:

455

Check: 405

473

361

- 50

+ 50

+ 361 is checked in this manner:

+ 473

405

455

834

834

NOTE: When more than two numbers are added together, there is more

than one way to rearrange the addends. The easiest may be to begin

with the bottom and add upward (with the top number being added last).

The term "adding up" comes from an older method in which the sum was

written at the top instead of the bottom.

NOTE: Filling in spaces with zeros can help to keep columns straight.

Solve and check:

34 + 121 + 87.

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Solution to

Just as subtraction problems can be checked using addition, so addition

Frame 1-27

problems can be checked using subtraction. Subtracting one addend

from the sum will yield the remaining addend. (This method of checking

242

11

is used less than the reverse adding method.)

34 Check: 034

121

121

Check: 473 + 361 = 834

+ 87

087

11

242

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Solution to

Division can be checked by multiplying the quotient (without the

Frame 1-28

remainder) by the divisor and adding the remainder (if any). The resulting

number will be the dividend. For example:

7 13

7 13

834

or

834

5

5

quotient

-473

-361

3/ 17

Check:

x3

divisor

361

473

15

15

2

+2

remainder

17

dividend

Solve and check this problem: 4,864 13.

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MD0900

1-12

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