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Grade 2 · lesson 2 of 4

Rename a Ten Before Subtracting Ones

Read the needed ones subtraction.

About 20 minutes, plus any extended practice

Download the grade pack

Supplied materials

  • Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
  • Supplied worked-case record: For 72−38, rename 72 as six tens and twelve ones.
  • All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

A subtraction can require more ones than the starting ones place shows. Rename one ten as ten ones before removing anything. The starting amount stays the same. Then subtract matching place units and use addition to check the difference.

Read the needed ones subtraction. If necessary exchange one starting ten for ten ones, reducing the tens count. Remove the ones and tens requested, then check difference plus removed amount equals the start.

After exchanging a ten, reduce the tens count by one. Check subtraction by adding the difference and the removed amount. Show the unchanged start in both its original and regrouped forms.

  1. Show the unchanged start in both its original and regrouped forms.
  2. Follow the worked example. Point to each number or shape feature and say what it tells you.
  3. Read the needed ones subtraction.
  4. Try the question and then the three practice questions. Check your answers and explain any change you make.
Worked example

See the method in action

For 72−38, rename 72 as six tens and twelve ones. Remove three tens and eight ones to leave three tens and four ones, or 34. Check 34+38=72. Keeping seven tens after the exchange would overstate the answer by ten. After exchanging a ten, reduce the tens count by one. Check subtraction by adding the difference and the removed amount. Show the unchanged start in both its original and regrouped forms.

Your turn

Check your reasoning

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Helpful tips
  • After exchanging a ten, reduce the tens count by one.
  • Check subtraction by adding the difference and the removed amount.
Subtract with a regrouping model: 62−27.

Feedback appears here after you check. This is practice, not a graded school assessment.

See the answer and explanation

35

Rename a ten as ten ones when needed, then subtract matching places. The result is 35.

Take it further

Find 83−46. Expected: 37; seven tens and thirteen ones before removal.

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More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. Subtract with a regrouping model: 72−28.
Need a hint?
  • After exchanging a ten, reduce the tens count by one.
  • Check subtraction by adding the difference and the removed amount.
2. Subtract with a regrouping model: 82−29.
Need a hint?
  • After exchanging a ten, reduce the tens count by one.
  • Check subtraction by adding the difference and the removed amount.
3. Subtract with a regrouping model: 92−30.
Need a hint?
  • After exchanging a ten, reduce the tens count by one.
  • Check subtraction by adding the difference and the removed amount.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

Check the subject sources

These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.