Year 4 - Maths
Reflect polygons in a line of symmetry
Properties of 2D and 3D shapes and symmetry
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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 reflect polygons in a line of symmetry, including when there are no sides parallel to the line of symmetry.
Key Notes
- When you reflect a shape, it will be the same distance from the mirror line on both sides.
- You can reflect a shape by counting the position of each vertex and making a mark, and then joining the marks.
Vocabulary To Learn
- Line of symmetry: If you were to fold a shape on its line of symmetry, both halves would match exactly.
- Mirror line: Another term for a line of symmetry. If you were to fold a shape on its line of symmetry, both halves would match exactly.
- Reflect: When you reflect a shape, you flip it over a mirror line or line of symmetry without turning it or changing the size.
- Reflection: The mirror image of a shape.
Common Mistakes To Avoid
- Children may translate or copy a shape rather than 'flipping it' over the line of symmetry.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When you reflect a shape, it will be the same distance from the mirror line on both sides. You can reflect a shape by counting the position of each vertex and making a mark, and then joining the marks.
2. Use this key word in a maths sentence and explain it clearly. 'Line of symmetry'
If you were to fold a shape on its line of symmetry, both halves would match exactly. 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 translate or copy a shape rather than 'flipping it' over the line of symmetry. Correction: Use mirrors to support children's understanding of how a shape flips when it is reflected. Explore this idea with a wide variety of shapes.
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
- Find lines of symmetry in 2D shapes 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 that are dissected by the line of symmetry Study Guide
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