Calculating missing side lengths from the area of a trapezium

You can calculate a missing side length from the area of a trapezium.

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Year 7

Calculating missing side lengths from the area of a trapezium

You can calculate a missing side length from the area of a trapezium.

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Share activities with pupils

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Lesson details

Key learning points

The formula can be used to calculate the area of a trapezium.
The area of a trapezium can be used to calculate a missing side length.
It cannot be used to calculate one of the slanted sides.

Keywords

Trapezium - A trapezium is a quadrilateral with exactly one pair of parallel opposite sides.
Trapezia/trapeziums - The plural of trapezium can be referred to as trapezia or trapeziums.

Common misconception

Pupils may forget to divide by 2 when calculating the area of a trapezium.

The area of a trapezium is half of the area of the parallelogram formed from two identical trapeziums.

In this lesson, one form of the area formula is used. You should use an alternative form if your pupils would be more comfortable doing so. This form was chosen as it allows pupils to practise simplifying fractions should they wish.

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Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).