Math · Stage 4
Fill grid and area puzzles from partial information
Every row, column and whole area has a fixed total — so one known total plus the cells you can see unlocks any missing piece.
✦ Math📘 Stage 4 · S4⏱ ~12 min🧒 Ages 8–9★ Free to start
I can fill grid and area puzzles from partial information.
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Kavi's Half-Hidden Grid 🔲
Kavi finds a puzzle grid with some cells smudged out ✨. "I don't guess the missing ones," hoots Kavi. "Every row and column adds to a fixed total, and the whole area is fixed too. If a line should total 20 and I can see 8 and 5, then the smudged cell must be 20 − 13 = 7. Partial clues are plenty — the fixed totals do the rest!"
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What your child will learn
1A fixed line total unlocks the missing cellIn a grid puzzle, a row (or column) must add to a fixed total. Here the line total is 20, and you can already see cells adding to 13. The number bond shows the rest: 20 is the whole, 13 is the part you can see.
2Subtract what you see from the totalTurn the clue into a subtraction. The line must total 20 and the visible cells add to 13. Tap Step → to work 20 − 13 and reveal the missing cell.
3A whole area is fixed too — find the missing regionA big 6 × 4 rectangle has area 6 × 4 = 24 squares. It is cut into 4 smaller rectangles. Three of the regions are known — their areas are 8, 6 and 4. Tap each card to see how the fixed whole area reveals the fourth.
4Know the bonds of 20, fill the grid fastEvery missing cell is a bond of the total in disguise. If the line total is 20 and the cells you see add to 14, the missing one is 6; if they add to 17, it is 3. The faster you know the bonds of the total, the faster the whole grid falls into place.
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A peek inside
A grid row must total 20. The row reads 8, ▢, 5. Find the missing cell.
see 8 and 5 → 8 + 5 = 13 · 20 − 13 = 7 · check: 8 + 7 + 5 = 20 ✓
Try this at home: A row must total 20. It shows 8, 5, __ . The missing cell is __
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 4 · S4 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.