# third grade math

posted by
**zeke** on
.

how do you check addition problems by adding up?

Let's use this addition problem as an example.

21

35

___

First you add 1 + 5. To check your work, add up, 5 + 1.

If you have a column of numbers and you go down each column to add them together, that's normal, right?

36

95
__15__

146

To check to make sure you're right, you'd add **from the bottom to the top** of each column. If you get the same answer, you know it's right.

15

95
__36__

146

That's called **adding up**.

When my mother was working for her father in the family business (long before calculators or computers) and had to add long columns of numbers, adding down was the standard; then adding up was the double-check.

=)

thank you.

thank you,that was very helpful.