Year 4 - Maths
Reflect polygons that are dissected by the 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 that are dissected (cut in half) by the line of symmetry, and explore the new shapes that are created when a polygon is reflected.
Key Notes
- When you reflect a shape, each vertex will be the same distance from the line of symmetry.
- When you reflect a polygon that has a side that is touching the mirror line, you can sometimes create a new shape.
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: Mirror line is another term to describe the line of symmetry.
- 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 reflection of a shape is the mirror image of a shape.
Common Mistakes To Avoid
- Children may miscount the number of squares from the mirror line when plotting each vertex to reflect the shape.
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, each vertex will be the same distance from the line of symmetry. When you reflect a polygon that has a side that is touching the mirror line, you can sometimes create a new shape.
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 miscount the number of squares from the mirror line when plotting each vertex to reflect the shape. Correction: Encourage children to work systematically by only marking one vertex at a time to reduce the chance of errors. Also encourage use of mirrors to check.
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 in a line of symmetry Study Guide
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