Year 4 - Maths
Find lines of symmetry in 2D shapes
Properties of 2D and 3D shapes and symmetry
Study Hub
Study Guides
This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will complete and compose symmetrical shapes from two congruent shapes and investigate lines of symmetry in 2D shapes.
Lesson Summary
You will learn to find lines of symmetry in 2D shapes and explain the link between lines of symmetry and number of sides in regular polygons.
Key Notes
- A line of symmetry splits the shape into two equal parts which are mirror images.
- Shapes are symmetrical when they look the same when a mirror is placed on the mirror line.
- Regular polygons have the same number of lines of symmetry as they have sides.
Vocabulary To Learn
- Symmetrical: When a shape, pattern or image has one half that is the reflection of the other half, it can be described as symmetrical.
- Line of symmetry: If you were to fold a shape on its line of symmetry, both halves would match exactly.
- Regular polygon: A regular polygon has sides that are all equal and angles that are all equal.
Common Mistakes To Avoid
- Children may not identify lines of symmetry that are neither horizontal nor vertical.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
A line of symmetry splits the shape into two equal parts which are mirror images. Shapes are symmetrical when they look the same when a mirror is placed on the mirror line.
2. Use this key word in a maths sentence and explain it clearly. 'Symmetrical'
When a shape, pattern or image has one half that is the reflection of the other half, it can be described as symmetrical. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Children may not identify lines of symmetry that are neither horizontal nor vertical. Correction: Allow opportunities for children to handle and manipulate cut outs of shapes so that they can try to find lines of symmetry in different orientations. Encourage them to describe the position of the line of symmetry to support their understanding.
More Lessons In This Unit
- Complete a symmetrical pattern Study Guide
- Diagonal lines of symmetry Study Guide
- Explore symmetry by joining two identical shapes Study Guide
- Explore, sort and classify triangles Study Guide
- Identify different types of triangle Study Guide
- Investigate lines of symmetry in 2D shapes by folding Study Guide
- Investigate symmetry and symmetrical patterns Study Guide
- Reflect polygons in a line of symmetry Study Guide
- Reflect polygons that are dissected by the line of symmetry Study Guide
Browse all guides in the Year 4 Maths guide library.