Year 4 - Maths
Calculate the side length of a regular polygon by division where the perimeter is known
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 division to calculate the side length of a regular polygon when the perimeter is known.
Key Notes
- If you know the perimeter of a regular polygon you can calculate the length of one side.
- Divide the perimeter by the number of sides to calculate the length of one side.
- Knowledge of times tables and related division facts can support calculation.
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 often find division a trickier concept than multiplication and do not connect this to their known multiplication facts.
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 perimeter of a regular polygon you can calculate the length of one side. Divide the perimeter by the number of sides to calculate the length of one side.
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 often find division a trickier concept than multiplication and do not connect this to their known multiplication facts. Correction: Establish the inverse relationship with multiplication and show how the division equations can be re-written as a multiplication equation with a missing factor. Support pupils in making this connection to allow them to use known facts to calculate.
More Lessons In This Unit
- 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
- Understand that the perimeter of a regular polygon can be calculated by multiplication Study Guide
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