Make the Sum: A Logic Puzzle Lesson on Reasoning With Numbers
Students solve target-sum puzzles by reasoning, explain one strategy in words, and check their answer.
Aligned to: CCSS MP.1 (make sense of problems and persevere) and 3.OA.D.8 (solve two-step problems).
Materials
- Paper plates or circles drawn on paper (the islands)
- Number cards 1–9
- The three puzzle cards below
Lesson steps
| 5 min | Warm-up. Write 3, 5 and 7 on the board. Which two make 12? Which three make 15? How did you know? |
| 10 min | Model. Draw two islands with targets 10 and 8, and the numbers 2, 3, 5 and 8 to share between them. Think aloud: 8 can't go with anything on the 8-island, so it must go alone there. Then 2, 3 and 5 make 10. |
| 15 min | Pairs: puzzle cards. Pairs solve the three puzzle cards using paper islands and number cards, writing each sum to check. |
| 10 min | Strategy talk. Share strategies: start with the biggest number, start with the island that has the fewest options, work backwards. |
| 5 min | Exit ticket. Students answer on their own. |
Cards to print and cut
Puzzle 1: Islands want 9 and 6. Numbers: 1, 4, 5, 5.
Puzzle 2: Islands want 12 and 7. Numbers: 2, 3, 5, 9.
Puzzle 3: Islands want 10, 10 and 5. Numbers: 1, 2, 3, 4, 6, 9.
Exit ticket
Name: ____________________
- Write one strategy that helped you.
- Make your own puzzle: two islands, four numbers. Swap with a partner.
Answer key and teacher notes
- Puzzle 1: 4 + 5 = 9 and 1 + 5 = 6.
- Puzzle 2: 3 + 9 = 12 and 2 + 5 = 7.
- Puzzle 3: 1 + 9 = 10, 4 + 6 = 10, 2 + 3 = 5.
Keep practising
Number Puzzles: Sumbriska
Number Puzzles: Sumbriska is a quiet puzzle game built on this exact idea: flip bridges to send numbers between islands until every island hits its target. Good for early finishers or a class challenge.
Get it free on the App StoreTeacher FAQ
Is this lesson plan free to use?
Yes. Print and copy it for your class or group. No sign-up.
How long does it take?
About 45 minutes, with timings for each part so you can trim it to fit.
What do I need?
Only everyday classroom materials, listed under Materials. No app or device is required to teach it.