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First/Addition

➕ Friendly Decomposition Addition

Break addends into friendly tens and hundreds, then add mentally.
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Study Guide

Preview

➕ Friendly Decomposition Addition preview

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Practice Questions

  1. 7 + 3 + 8 + 2 = ?
    Show answer

    20

  2. 6 + 4 + 9 + 1 = ?
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    20

  3. 25 + 75 + 18 + 32 = ?
    Show answer

    150

  4. 40 + 60 + 22 + 28 = ?
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    150

  5. 45 + 55 + 65 + 35 = ?
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    200

Teacher Resources
Teaching Notes

Model pairing then partial sums.

Common Mistakes
  • Wrong pair total
  • Incorrect decomposition.
  • Forgetting remaining value.
  • Misidentifying benchmark target.
  • Adding partial sums incorrectly.
Differentiation
SupportUse manipulatives or number lines for decomposition.
ChallengeExtend to larger numbers or include multiple addends.
Discussion Questions
  • Why is making a ten or hundred helpful?
  • How does this strategy support mental math?
  • When is this decomposition strategy most useful?
  • Can you explain another addition strategy?
Learning Path
Skill Cluster

Number Sense & Operations

Estimated Time

12 minutes

Skills Practiced
Benchmark groupingMental chunking