Year 4 - Maths
Understand that the perimeter of a regular polygon can be calculated by multiplication
Perimeter
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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 pupil will learn perimeter as the distance around the edge of a 2D shape. They will learn perimeter is measured in units of length found by counting units and by calculating by adding the side lengths of a 2D shape.
Lesson Summary
You will learn to calculate the perimeter of a regular polygon using multiplication.
Key Notes
- If you know the length of one side of a regular polygon you can calculate the perimeter.
- Multiply the side length by the number of sides of the regular polygon to calculate the perimeter.
Vocabulary To Learn
- Perimeter: The distance around a two-dimensional shape.
- Regular: A regular polygon has all sides equal and all angles equal.
Common Mistakes To Avoid
- Pupils may overgeneralise and assume all perimeters can be calculated by multiplying one side length by the number of sides in the polygon.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
If you know the length of one side of a regular polygon you can calculate the perimeter. Multiply the side length by the number of sides of the regular polygon to calculate the perimeter.
2. Use this key word in a maths sentence and explain it clearly. 'Perimeter'
The distance around a two-dimensional shape. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils may overgeneralise and assume all perimeters can be calculated by multiplying one side length by the number of sides in the polygon. Correction: 'Noticing' is a key mathematical skill. Encourage pupils to take their time to notice whether the shape is regular or irregular, if that information is not already explicitly given.
More Lessons In This Unit
- Calculate the side length of a regular polygon by division where the perimeter is known Study Guide
- Know that a regular polygon has sides that are the same length and angles that are the same size Study Guide
- Know that perimeter can be calculated by adding together the side lengths of a 2D shape Study Guide
- Know that perimeter is measured in units of length and can be found by counting or measuring units Study Guide
- Know that the perimeter is the distance around a 2D shape Study Guide
- Know that the perimeter of a rectangle can be calculated by addition and multiplication Study Guide
- Know that unknown side lengths can be calculated from the perimeter and known side lengths Study Guide
- Solve problems involving the perimeter and side lengths of polygons Study Guide
- Understand that different shapes can have the same perimeter Study Guide
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