Lines of Symmetry | Math Mystery Worksheets | Grades 3–4 | Complete the Figure

Five detective cases turn symmetry into something students have to finish, not just spot — the dashed line on each grid is the fold, and it never cuts a shaded square in half. Students flip the shading across it, count the squares, write the answer, match it to a suspect, and cross suspects off until one is left standing. The fold moves as the cases go on, which is what makes it harder than it looks.

Quick Details

Skill: Lines of symmetry and completing a symmetrical figure · Grades: 3–4 · Format: 5 mysteries in difficulty order + full answer keys (printable PDF) · Theme: Around the school

The 5 Mysteries

The Mirror Mural — Half of every mural has been washed off; flip the shaded squares across the fold and count them all.

The Missing Halves — Somebody stopped halfway through copying each bookmark, so students count the shaded squares with no matching partner.

The Flipped Lab Tray — The fold now runs across the grid rather than down it.

The Backwards Banner — The shading sits on the right of the fold, so it flips left instead.

The Canteen Cut-Outs — The cut-outs are folded every which way, so students have to find the fold first.

Why Teachers Love It

Zero prep — print and teach. The built-in answer keys make every case self-checking, so students get instant feedback and stay motivated. Moving the fold from vertical to horizontal to unknown is the difference between a student who has memorised one picture and one who actually understands reflection — and squared paper or a small mirror is all the support a struggling student needs.

Skills Covered

Identifying a line of symmetry, completing a symmetrical figure on a grid, reflecting across vertical, horizontal and non-obvious folds, counting squares, and recognising which squares have no matching partner — plus logical reasoning and deductive elimination as students rule suspects out clue by clue.

What's Included

Printable one-page mystery worksheets, a grid figure and fold line on every problem, suspect line-ups, complete answer keys with the villain marked, and student instructions — all in one PDF.

Best Used For

Symmetry and geometry practice in math centers, morning work, homework, early finishers, substitute/relief days, indoor recess, spiral review, and test prep for grades 3–4.

More From This Line

Browse every Math Mystery pack, or carry on with Area and Perimeter and 4th Grade Review.