Year 7 - Maths
Perimeter with composite rectilinear shapes
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 the perimeters of compound shapes, including generalising a perimeter formula where appropriate.
Key Notes
- You can identify how to find the perimeter of compound shapes made of rectangles.
- You can calculate the perimeter of compound shapes made from rectangles.
- You can generalise the perimeter of compound shapes made of rectangles.
- It is possible to find missing lengths in compound shapes made from rectangles.
Vocabulary To Learn
- Compound shape: A compound shape is a shape created using two or more basic shapes.
- Composite shape: A composite shape is an alternative term for a compound shape.
- Composite rectilinear shape: A composite rectilinear shape is a composite shape made from rectangles.
Common Mistakes To Avoid
- Pupils may think they can always double the length and width to calculate the perimeter.
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 compound shapes made of rectangles. You can calculate the perimeter of compound shapes made from rectangles.
2. Use this key word in a maths sentence and explain it clearly. 'Compound shape'
A compound shape is a shape created using two or more basic shapes. 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 they can always double the length and width to calculate the perimeter. Correction: This only works for composite rectilinear shapes if the lengths do not overlap.
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
- Finding the perimeter of polygons 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.