Mirror-line grid puzzle
Complete a pattern by mapping cell centres across a vertical mirror line.
Lower primary · about 6–9 · Shape & spatial thinking · Logic & rule checking · Cooperation & communication
- Players
- Pairs
- Plan for
- 10–15 minutes
- Bring
- Per pair: one 6×4 grid, pencil and optionally large paper markers. Mirror line lies between columns C and D.
30 pupils: fifteen pairs; one maps a cell, one checks distance from the mirror line, then swap.
Prepare
Label columns A–F left to right and rows 1–4 bottom to top. Mirror line is the shared edge between C and D, not a column of cells. Shade A1, B3, C2 and C4 on the left. Leave the right half blank.
Play
For each shaded left cell, shade the right cell in the same row with its centre equally far from the line. Near-line C maps to D, B to E, A to F. Take turns pointing and checking; do not slide the pattern one column.
Example
A1 maps to F1, B3 to E3, C2 to D2, C4 to D4. Rows do not reverse across a vertical line. Count each cell centre’s steps from the middle to justify a pair.
Finish
Four correct right cells with no extra marks completes the supplied puzzle. Compare with the teacher key only after trying. A new left-half pattern can make a second puzzle; write down its key before sharing.
Adapt
Start with C2 alone, use coloured large markers or have a partner shade the chosen cell. A horizontal-axis or diagonal task is a different version and is not used on this sheet.
Purpose and provenance
Activity aim: Complete a pattern by mapping cell centres across a vertical mirror line.
Practice opportunities: Comparing perpendicular distance from a line and checking corresponding row positions.
What adults can observe: Ask the child to explain near/far from the line, not just copy a teacher answer.
Mechanism and our adaptation: PartyPageKit classroom adaptation of a common activity mechanism. The earliest inventor has not been established; the linked references are identified separately by the editor.
Reference: University of Cambridge NRICH — Let Us Reflect — Related line-reflection teaching background; our coordinate-grid problem and key do not reproduce the mirror task.
These are planning aims and observable actions, not measured lasting gains. The reference is not an endorsement or a test of our adaptation.
Free material alternatives: Draw six columns and four rows on scrap paper; fold along the middle only to check after attempting.
Buying links: reserved; no purchase is required.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. Use only the pages needed for the chosen version; oral and movement activities may need no printing.
Player mirror-line grid
Shade only the matching right-half cells. Mirror line is between C and D. Match cell centres at equal distances, in the same row.
Player mapping record
| Given | Partner cell | Reason |
|---|---|---|
| A1 | ________ | ________ |
| B3 | ________ | ________ |
| C2 | ________ | ________ |
| C4 | ________ | ________ |
Teacher instructions and key · keep separate
30 pupils: fifteen pairs; one maps a cell, one checks distance from the mirror line, then swap.
Per pair: one 6×4 grid, pencil and optionally large paper markers. Mirror line lies between columns C and D.
Draw six columns and four rows on scrap paper; fold along the middle only to check after attempting.
Preview one copy. Print only required player pages; keep this teacher page out of player packets. Give children the choice to watch, pause or use the described adaptation. These are activity practice opportunities, not measured developmental outcomes.
Key: A1→F1, B3→E3, C2→D2, C4→D4. Mapping column index c to 7−c preserves row.