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Checking Your Work with Addition
“I know I sometimes make mistakes when I subtract. So I want a good way to check my answers,” said Kathy.
“I use addition to check,” said Sara. “In a subtraction problem, I start with a number and subtract something. If I add back what I subtracted, I should get the number that I started with. If I do not, I must have made a mistake.”
Kathy used Sara's method to do the problem 621 − 293. Her answer was 332.
She used addition to check her answer.
- Kathy used addition to check these answers. Which are correct and which are incorrect? Tell how you know.
For more practice, use the Checking with Addition page in the Student Activity Book.