Year 7 - Maths
Area of a triangle
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 derive the formula for the area of a triangle.
Key Notes
- It is possible to find a relationship between triangles and parallelograms.
- You can use this relationship to find a formula for the area of a triangle.
- It is possible to identify the base and perpendicular height of any triangle even when they are not obvious.
- The formula can be used to find the area of any triangle.
Vocabulary To Learn
- Base: The base is the side which is perpendicular to the height.
- Perpendicular height: The perpendicular height is the perpendicular distance from the base to the opposite vertex.
Common Mistakes To Avoid
- Pupils may forget to halve after multiplying the base and the perpendicular height.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
It is possible to find a relationship between triangles and parallelograms. You can use this relationship to find a formula for the area of a triangle.
2. Use this key word in a maths sentence and explain it clearly. 'Base'
The base is the side which is perpendicular to the height. 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 forget to halve after multiplying the base and the perpendicular height. Correction: The area of a triangle is equal to half the area of the parallelogram formed by two of those triangles.
More Lessons In This Unit
- Area of a trapezium 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
- 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.