Year 7 - Maths
Using the formula for the 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 use the formula for the area of a triangle to calculate missing side lengths.
Key Notes
- 0.5 x base x perpendicular height can be used to find the area of any triangle.
- Missing sides can be found if the area is known.
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 think the height of the triangle is the slanted height rather than perpendicular.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
0.5 x base x perpendicular height can be used to find the area of any triangle. Missing sides can be found if the area is known.
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 think the height of the triangle is the slanted height rather than perpendicular. Correction: The base and height to be used must be perpendicular (at a right angle) to each other.
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
- Perimeter with composite rectilinear shapes Study Guide
- Problem solving with perimeter and area Study Guide
- Securing understanding of perimeter and area Study Guide
Browse all guides in the Year 7 Maths guide library.