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Grade 2 · unit review

Review: Explain Regrouping and Two-Step Stories

Regroup in addition and subtraction, adjust mental sums, and keep two story changes separate.

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Bring the unit skills together

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Unit review questions
1. Add using place-value regrouping: 186+132.
Need a hint?
  • Add the exchanged group into its new place.
  • Regrouping preserves value; it does not create an extra amount.
2. Subtract with a regrouping model: 102−31.
Need a hint?
  • After exchanging a ten, reduce the tens count by one.
  • Check subtraction by adding the difference and the removed amount.
3. Use a friendly ten to calculate 39+29.
Need a hint?
  • Write the temporary extra amount so you remember to correct it.
  • If you rounded an addend up, correct the sum downward.
4. A box starts with 52 cards, receives 16, and gives away 23. How many remain?
Need a hint?
  • Write the intermediate total between the two operations.
  • A result after the first change is not the final answer.

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Find 263−78 using a base-ten model and check the answer.

Work on paper or in your own document. Explain the choices you made.

  • Draw or label the numbers or shape features the task gives you.
  • Say why each calculation or shape choice follows the ideas in this unit.
  • Check that your answer fits the story or drawing in the task.
Compare with a model response

Rename 263 as two hundreds, five tens, thirteen ones. Subtract seven tens and eight ones by also renaming a hundred: one hundred, fifteen tens, thirteen ones. Result: 185; 185+78=263.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.