Use the area of a triangle to calculate unknown measurements
I can calculate unknown dimensions of a triangle with a specified area.
Use the area of a triangle to calculate unknown measurements
I can calculate unknown dimensions of a triangle with a specified area.
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Lesson details
Key learning points
- The area of a triangle is half the area of a parallelogram with the same perpendicular base and height.
- The area of a triangle can be calculated using the formula area = base × perpendicular height ÷ 2
- A missing perpendicular height in a triangle can be found using the formula area × 2 ÷ base
- A missing base in a triangle can be found using the formula area × 2 ÷ perpendicular height
Keywords
Base - The base is the side which is perpendicular to the shape’s height.
Perpendicular - Two lines are perpendicular if they meet at a right angle.
Common misconception
When drawing triangles with a given area pupils may create a factor pair of the triangle's area when drawing the base and perpendicular height. The factor pair refers to the surrounding parallelogram.
For pupils who are making this mistake, encourage them to sketch the parallelogram around the triangle, reminding them to double the triangle area before finding the factor pairs.
To help you plan your year 6 maths lesson on: Use the area of a triangle to calculate unknown measurements, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 6 maths lesson on: Use the area of a triangle to calculate unknown measurements, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
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Explore more key stage 2 maths lessons from the Area, perimeter, position and direction unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
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Lesson video
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Starter quiz
6 Questions
Exit quiz
6 Questions
