Thinkabara

🧮 2nd Grade · Math2.NBT.B.9Unit 5: Subtracting within 100

Check with addition

Google Classroom

🎯 Objective: Students check subtraction answers by adding and explain why it works.

Lesson outline

  1. Solve 64 − 29 and check: 35 + 29.
  2. Explain the part-part-whole link.
  3. Find mistakes in sample work.
  4. Exit: solve and check.

Lesson 4 of 5 in this unit. In the Lesson Planner this lesson takes 1–3 class periods depending on your timetable: day 1 introduce & model, then practice, small-group reteach and a quick check.

📐 Standard

2.NBT.B.9

Common Core State Standards for Mathematics, Grade 2 — typical US scope & sequence

🏁 Unit goals

  • Subtract two-digit numbers using place value strategies
  • Check subtraction with addition

✅ Check for understanding

End with the exit ticket in the outline. Sort answers into got it / almost / not yet and start the next lesson with a 5-minute reteach for the “not yets”.

Practice & resources on Thinkabara

🎯 Practice: Add & subtract within 100🎯 Practice: Place value to 1,000🖨️ Worksheet: Two-Digit Addition Within 100🖨️ Worksheet: Two-Digit Subtraction Within 100📚 All 2nd Grade skills🎮 Learning games⚡ Capy Live class quiz

🗓️ Plan the whole year like this

Add 2nd Grade Math to your free Lesson Planner: enter your timetable once and every period shows the next lesson, skipping weekends and school breaks.

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More lessons in “Subtracting within 100”

  1. Subtracting tens and ones
  2. Regrouping a ten
  3. Counting up to subtract
  4. Check with addition
  5. Subtraction word problems

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