Year 7 - Maths
Calculating missing side lengths from the area of 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 calculate a missing side length from the area of a composite rectilinear shape.
Key Notes
- Given the area, it is possible to calculate a missing side length.
- The most efficient method may depend on the features of the shape.
Vocabulary To Learn
- Composite rectilinear shape: A composite rectilinear shape is a composite shape made from rectangles.
Common Mistakes To Avoid
- Pupils may try to combine lengths that are not parallel to a known side length.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Given the area, it is possible to calculate a missing side length. The most efficient method may depend on the features of the shape.
2. Use this key word in a maths sentence and explain it clearly. 'Composite rectilinear shape'
A composite rectilinear shape is a composite shape made from rectangles. 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 try to combine lengths that are not parallel to a known side length. Correction: For two sets of side lengths to be equal, one set must be parallel to the other and none of the lengths can 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
- Checking understanding of perimeter and area Study Guide
- Finding the perimeter of polygons 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.