Thinkabara

🧮 4th Grade · Math4.OA.B.4Unit 3: Multiplicative comparison, factors & multiples

Prime and composite

Google Classroom

🎯 Objective: Students classify numbers to 100 as prime or composite.

Lesson outline

  1. Sieve of Eratosthenes on a hundred chart: cross out multiples of 2, 3, 5, 7.
  2. Define prime (exactly two factors) and composite; discuss why 1 is neither.
  3. Sort numbers 1–50.
  4. Exit: is 51 prime? Explain.

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

4.OA.B.4

Common Core State Standards for Mathematics, Grade 4 — typical US scope & sequence

🏁 Unit goals

  • Interpret multiplication as comparison (35 is 5 times as many as 7)
  • Find factor pairs and multiples; identify prime and composite numbers

✅ 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

📚 All 4th Grade skills🎮 Learning games⚡ Capy Live class quiz

🗓️ Plan the whole year like this

Add 4th Grade Math to your free Lesson Planner: enter your timetable once and every period shows the next lesson, skipping weekends and school breaks.

Add to my planner See the year’s sequence

More lessons in “Multiplicative comparison, factors & multiples”

  1. Times as many
  2. Comparison word problems
  3. Factors and factor pairs
  4. Multiples
  5. Prime and composite

Something to improve in this lesson? Tell us.