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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
New
New
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.

Download all resources
Share activities with pupils

Lesson details

Key learning points

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

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.

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.

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.
Teacher tip

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).

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Starter quiz

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6 Questions

Q1.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 29.75, 29.75 cm$$^2$$
Q2.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 32, 32 cm$$^2$$
Q3.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 46, 46 cm$$^2$$
Q4.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 56, 56 cm$$^2$$
Q5.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 77, 77 cm$$^2$$
Q6.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 34.5, 34.5 cm$$^2$$

Exit quiz

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6 Questions

Q1.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 10, 10 cm$$^2$$
Q2.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 13.125, 13.125 cm$$^2$$
Q3.
Calculate the area of the trapezium (you do not need to state the units).
An image in a quiz
Correct Answer: 9.35, 9.35 cm$$^2$$
Q4.
What is the value of $$b$$?
An image in a quiz
Correct answer: 4
14
16
32
Q5.
What is the value of $$d$$?
An image in a quiz
5
5.5
6
Correct answer: 7
Q6.
What is the value of $$h$$?
An image in a quiz
3
5
9
Correct answer: 11