Thinkabara

🧮 1st Grade · Math1.OA.A.1Unit 2: Story problems within 20

Change unknown

Google Classroom

🎯 Objective: Students solve problems where the change is unknown (5 + ? = 12).

Lesson outline

  1. Act out: 5 kids on the bus, some more get on, now 12.
  2. Model counting on from 5 to 12.
  3. Solve change-unknown problems with a number line.
  4. Exit: write an equation with a box for the unknown.

Lesson 3 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.A.1

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

🏁 Unit goals

  • Solve add-to, take-from, put-together and compare problems
  • Represent problems with drawings and equations with a symbol for the unknown

✅ 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 “Story problems within 20”

  1. Add-to and take-from stories
  2. Put-together and take-apart
  3. Change unknown
  4. Compare problems
  5. Adding three numbers

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