Year 4 - Maths
Solve problems involving the perimeter and side lengths of polygons
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 use knowledge of side lengths and perimeter to solve problems.
Key Notes
- Perimeter is the sum of the side lengths of a 2D shape.
- Mental and written methods can be used to calculate the perimeter of a 2D shape.
- Combinations of addition, subtraction, multiplication and division can be used to solve problems involving 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 think that if they know the perimeter of a shape, and a new shape has been made from duplicates of it, they can simply multiply the perimeter by how many shapes make up the new one.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Perimeter is the sum of the side lengths of a 2D shape. Mental and written methods can be used to calculate the perimeter of a 2D shape.
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 think that if they know the perimeter of a shape, and a new shape has been made from duplicates of it, they can simply multiply the perimeter by how many shapes make up the new one. Correction: The lesson highlights this misconception and tackles it but it is worth being aware of it as pupils work. Point out to them that some of the sides from the original shape are now inside the new shapes so do not count as part of its perimeter.
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
- Understand that different shapes can have the same perimeter Study Guide
- Understand that the perimeter of a regular polygon can be calculated by multiplication Study Guide
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