My First Logic Grid: One Check per Row
- Grade band
- 3
- Duration
- 40 minutes
- Skill
- The elimination rule in logic grid puzzles
- Standards
- RI.3.1 — Ask and answer questions to demonstrate understanding of a text, referring explicitly to the text as the basis for the answers.
- MP.7 — Look for and make use of structure.
- Materials
- Student worksheet (printable, included)
- Pencils with erasers
Learning objectives
- Students will be able to explain the grid rule: each row and each column has exactly one ✓.
- Students will be able to apply the rule to fill in every ✗ that a single ✓ creates, and to find a ✓ when only one box in a row or column is left.
- Students will be able to justify each mark in a solved grid by citing the clue number (or the grid rule) that proves it.
Lesson procedure
- Hook (4 minutes) — I Do. Show a solved 3×3 grid with only ✓ marks. Ask: “What do you notice about where the checks are?” Guide students to see that there's exactly one ✓ in every row and every column — because each person has exactly one thing, and each thing belongs to exactly one person.
- The ✓ spreads ✗s (6 minutes) — I Do. Draw an empty 3×3 grid, put one ✓ in it, and think aloud: “This ✓ means every other box in its row is ✗, and every other box in its column is ✗.” Fill them in. Name the move: cross out the row and column.
- Rule practice (7 minutes) — We Do. Work through Part 1 together. For grid B, ask: “Where is the only empty box left in the top row?” Name the second move: last box standing gets the ✓.
- Band puzzle (8 minutes) — We Do. Solve Part 2 as a class. After every mark, ask “Clue or rule?” and have students write a small number (clue) or an R (rule) in the corner of the box.
- Lunch puzzle (12 minutes) — You Do. Students solve the 4×4 puzzle in Part 3 independently, then answer the “prove it” questions by citing clues.
- Exit ticket (3 minutes) — Closure. Students finish the sentence: “When I put a ✓ in a box, I also know that…”
Printable worksheet
Part 1: Use the grid rule. Every row and every column gets exactly ONE ✓. Fill in every ✗ you can. If only one box is left in a row or column, give it a ✓.
Grid A (one ✓ is given)
| hat | scarf | mittens | |
|---|---|---|---|
| Rosa | ✓ | ||
| Max | |||
| June |
Grid B (some ✗s are given)
| bike | scooter | skates | |
|---|---|---|---|
| Ivan | ✗ | ✗ | |
| Kim | ✗ | ||
| Lola |
Part 2: The band puzzle. Each student plays one instrument.
- Omar plays the flute.
- Tess does not play the drum.
| 🥁 drum | 🪈 flute | 🎹 piano | |
|---|---|---|---|
| Nia | |||
| Omar | |||
| Tess |
Part 3: The lunch puzzle (4×4). Each friend ate a different lunch.
- Ava ate the soup.
- Ben did not eat pizza.
- Ben did not eat salad.
- Cora did not eat pizza.
| 🍕 pizza | 🌮 tacos | 🍲 soup | 🥗 salad | |
|---|---|---|---|---|
| Ava | ||||
| Ben | ||||
| Cora | ||||
| Dev |
Prove it. Answer each question. Write the clue numbers (and “grid rule” if you used it) that prove your answer.
1. What did Ben eat? Proof:
2. Who ate the pizza? Proof:
3. No clue mentions Dev. How can you still be sure what Dev ate?
Background for the teacher
A logic grid works because the puzzle is a one-to-one matching: every person gets exactly one item, and every item goes to exactly one person. That structure is what makes the grid more than a chart — a single ✓ instantly rules out every other box in its row and column, and a row or column with only one open box forces a ✓. These two moves do most of the work in any grid puzzle; the clues just get them started.
Students often treat the grid as a place to record answers they already worked out in their heads. Push the opposite habit: make a mark, then look at the grid to see what it unlocks. Asking “clue or rule?” for every mark makes that thinking visible, and it gives you a fast way to spot where a student guessed. In the 4×4 puzzle, Dev is never mentioned, which is a natural opening for students to explain how the structure — not a clue — proves his answer.
Differentiation
Support: Have students use two colors: one color for marks that come straight from a clue, another for marks that come from the grid rule. Let them solve the 4×4 with a partner.
Extension: Ask students to find the fewest clues the lunch puzzle needs. (Can any clue be removed and still leave exactly one answer? Have them test it.)
ELL support: Pre-teach “row,” “column,” and “each” with a hand gesture (sweep sideways for row, up and down for column). Picture labels on the grid headings support the food and instrument vocabulary.
IEP/504 support: Provide an enlarged copy of the 4×4 grid, and allow students to give the “prove it” answers orally. Reduce Part 1 to Grid A only.
Answer key (for teachers)
Part 1 — Grid A. Rosa: scarf (given). ✗ in Rosa's hat and mittens, and in Max's and June's scarf boxes. Max and June's hat/mittens stay open — the rule alone can't decide them (a good discussion point: you need another clue).
Part 1 — Grid B. Ivan: skates (last box in his row). Then Kim's skates box is ✗, leaving Kim: bike. Lola: scooter (last box in her row, and the only open box in the scooter column).
Part 2 — Band. Nia: drum · Omar: flute · Tess: piano.
Part 3 — Lunch. Ava: soup · Ben: tacos · Cora: salad · Dev: pizza.
1. Ben ate tacos — Clues 2 and 3 rule out pizza and salad, and Clue 1 means soup is Ava's (grid rule).
2. Dev ate the pizza — Clues 2 and 4 rule out Ben and Cora, and Ava has soup (Clue 1), so the pizza column has one box left (grid rule).
3. Accept answers explaining that the other three lunches were already matched, so the grid rule leaves only one box in Dev's row.
Digital extension (optional)
Ready for more? Try a case in Sleuth Scouts. Cadet cases are 3×3 and Scout cases are 4×4, and the grid works exactly like today's worksheet — tap to mark ✓ and ✗, with the clue list alongside.