Year 7 - Maths
Finding the perimeter of polygons
Perimeter and area
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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 investigate how to calculate the area and perimeter of rectilinear shapes, and composite shapes using rectangles and triangles. They will also derive simple area formulae.
Lesson Summary
You will learn to use the properties of a range of polygons to deduce their perimeters, including generalising a perimeter formula where appropriate.
Key Notes
- You can identify how to find the perimeter of polygons.
- The perimeter of any polygon can be found by adding but this may be time consuming.
- You can use a formula to find the perimeter of rectangle.
- You can find and use a formula to find the perimeter of any regular polygon.
Vocabulary To Learn
- Polygon: A polygon is a flat (2D), closed figure made up of straight line segments.
- Perimeter: The perimeter is the distance around a 2D shape.
Common Mistakes To Avoid
- Pupils may not count all sides when calculating the perimeter due to the complexity of the shape.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
You can identify how to find the perimeter of polygons. The perimeter of any polygon can be found by adding but this may be time consuming.
2. Use this key word in a maths sentence and explain it clearly. 'Polygon'
A polygon is a flat (2D), closed figure made up of straight line segments. 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 not count all sides when calculating the perimeter due to the complexity of the shape. Correction: Encourage pupils to mark the sides as they record the measurement to ensure they count every side length.
More Lessons In This Unit
- Area of a trapezium Study Guide
- Area of a triangle Study Guide
- Area of composite rectilinear shapes Study Guide
- Calculating missing lengths with perimeter of polygons Study Guide
- Calculating missing side lengths from the area of a trapezium Study Guide
- Calculating missing side lengths from the area of composite rectilinear shapes Study Guide
- Checking understanding of perimeter and area Study Guide
- Perimeter with composite rectilinear shapes Study Guide
- Problem solving with perimeter and area Study Guide
- Securing understanding of perimeter and area Study Guide
- Using the formula for the area of a triangle Study Guide
Browse all guides in the Year 7 Maths guide library.