Area of triangles, parallelograms and trapeziums - Perimeter and area - WJEC - GCSE Maths Numeracy (WJEC) Revision

Area using formulas for triangles, parallelogram and trapezium

\(\text {Area of a triangle =}~\frac{1}{2} \times \text {base} \times \text {height}\)

This can also be written as:

\(\text {Area = base × height ÷ 2}\)

or

\(\text {Area =}~\frac {base \times height} {2}\)

The height is always the distance from the base to the top of the triangle.

A gardener wants to seed a triangular flowerbed.

Each pack of seed covers 600 cm². How many packs must be bought?

A parallelogram is a with two pairs of parallel sides. The opposite pairs of sides are equal in length.

\(\text {Area of a parallelogram = base × height}\)

The height is the perpendicular distance from the base to the top of the shape.

As with the rectangle we can use division to calculate one of the lengths given the area:

A company logo is a parallelogram with an area of 20 cm². What are the possible dimensions of the base and the perpendicular height?

A trapezium is a quadrilateral with one pair of parallel sides.

This formula will be given to you in the exam:

\(\text {Area of a trapezium =}~\frac{1}{2}({a+b}) \text{h}\)

Where a and b are the lengths of the parallel sides and the height is the perpendicular distance between them.

Calculate the area of the trapezium.