Year 3 - Maths
Investigate different ways of decomposing a polygon
Parallel and perpendicular sides in polygons
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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 investigate ways to compose and decompose polygons. They will investigate quadrilaterals with and without parallel and perpendicular sides.
Lesson Summary
You will learn to decompose a polygon in different ways and identify properties of polygons.
Key Notes
- The same whole can be split into different parts.
- Lines are perpendicular when they are at right angles to each other.
- Lines are parallel because they are always the same distance apart.
Vocabulary To Learn
- Polygon: A polygon is a 2D shape made up of three or more straight lines.
- Quadrilateral: A quadrilateral is a polygon that has four straight sides and four vertices.
- Parallel: Parallel lines are straight lines that are always the same distance apart. They never get closer together or further apart.
- Decompose: To decompose means to break something into parts that are the same as the original when you put them back together.
Common Mistakes To Avoid
- Pupils are not able to identify right angles and therefore struggle to identify pairs of perpendicular sides.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
The same whole can be split into different parts. Lines are perpendicular when they are at right angles to each other.
2. Use this key word in a maths sentence and explain it clearly. 'Polygon'
A polygon is a 2D shape made up of three or more straight lines. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils are not able to identify right angles and therefore struggle to identify pairs of perpendicular sides. Correction: Provide children with a right angle checker. Take time to model its use, focusing on aligning one edge of the checker with a side of the angle they want to check.
More Lessons In This Unit
- Construct quadrilaterals with and without parallel and perpendicular sides Study Guide
- Draw polygons on isometric paper Study Guide
- Draw shapes with given properties Study Guide
- Draw shapes with given properties on a range of geometric grids Study Guide
- Identifying parallel lines Study Guide
- Make and draw quadrilaterals on circular geoboards Study Guide
- Make and draw shapes with and without parallel and perpendicular sides Study Guide
- Make and draw triangles on circular geoboards Study Guide
- Make shapes by joining two polygons in different ways Study Guide
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