Math lesson plan · 4th grade (Year 5 in England) · 45 minutes
Lines of symmetry
Geometry
CCSS 4.G.A.3England: Y2 GeometryEngland: Y4 Geometry
Objective and success criteria
Students will: Lines of symmetry.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Polygons: sides and vertices
Leads to: Reflect points in a horizontal or vertical mirror line
Materials: Rulers and protractors, Squared or dotted paper, Shape cut-outs, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Polygons: sides and vertices). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- How many sides do a rectangle and a triangle have altogether? → 7Prompt: How many sides does a rectangle have?
- How many sides do a octagon and a hexagon have altogether? → 14Prompt: How many sides does a octagon have?
- How many sides do a triangle and a pentagon have altogether? → 8Prompt: How many sides does a triangle have?
Hook · 5 min
- Show a photo of a building, a tile pattern or a road sign and ask what shapes and angles students can spot.
- Share the objective: Lines of symmetry. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: How many lines of symmetry does a regular pentagon have?
- Step 1: A regular pentagon has 5.
- Answer: 5
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- How many lines of symmetry does an isosceles triangle (not equilateral) have? → 1Prompt: A line of symmetry folds the shape into two matching halves.
- Which capital letter has a vertical line of symmetry: N, T, Z, R? (Z / R / T / N) → TPrompt: Imagine a mirror standing straight up through the middle of the letter.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Which capital letter has a vertical line of symmetry: O, S, N, L? (S / N / O / L) → OPrompt: Imagine a mirror standing straight up through the middle of the letter.
- How many lines of symmetry does a square have? → 4Prompt: A line of symmetry folds the shape into two matching halves.
Watch out for
- Thinking a square turned on its corner is no longer a square.
- Reading the wrong scale on a protractor.
Support and stretch
Support
- Review first: Polygons: sides and vertices.
- Use concrete materials: rulers and protractors.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Reflect points in a horizontal or vertical mirror line.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-4.
Free lesson plan from eurekami.com/lesson-plan-builder