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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 Maruta.
“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 back the number that I started with. If I don't, I must have made a mistake.”
“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 back the number that I started with. If I don't, I must have made a mistake.”
Maruta used Sara's method to check her answer to 721 − 293. Her answer was 572.
She used addition to check her answer.
- Maruta used addition to check these answers. Which are correct and which are incorrect? Tell how you know.
Solve the subtraction problems in the Checking with Addition pages of your Student Activity Book. Use addition to check your answers.