Thinkabara

🧮 1st Grade · Math1.OA.D.8Unit 3: Addition strategies within 20

Missing addends

Google Classroom

🎯 Objective: Students find the unknown number in equations like 8 + ? = 11.

Lesson outline

  1. Hide counters: 8 showing, 11 in total.
  2. Model counting up from 8.
  3. Solve missing-addend equations on whiteboards.
  4. Exit: ? + 5 = 13.

Lesson 5 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

1.OA.D.8

Common Core State Standards for Mathematics, Grade 1 — typical US scope & sequence

🏁 Unit goals

  • Add within 20 using counting on, make-a-ten and doubles plus one
  • Explain the strategy you used

✅ 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 20🖨️ Worksheet: Addition Within 20🖨️ Worksheet: Subtraction Within 20📚 All 1st Grade skills🎮 Learning games⚡ Capy Live class quiz

🗓️ Plan the whole year like this

Add 1st 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 “Addition strategies within 20”

  1. Make a ten to add
  2. Doubles plus one
  3. Choosing a strategy
  4. Addition facts to 20 fluency
  5. Missing addends

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