third grade math

posted by zeke

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.

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