大象传媒

Two-dimensional shapes Area of compound shapes

Two-dimensional shapes are flat. The perimeter of a 2D shape is the total distance around the outside of the shape. The area of a 2D shape is the space inside the shape. Compound shapes can be split into different shapes to work out total area.

Part of MathsMeasurement

Area of compound shapes

The area of a compound shape can be calculated by adding the areas of the shapes it is made from.

Example

Calculate the area of the compound shape.

Side dimensions of the U shape

Method 1

Calculate the area of the large rectangle.

Area of the compound shape with side dimensions labelled

\(8 \times (4 + 4 + 4) = 8 \times 12 = 96~\text{cm}^2\)

Calculate the area of the square which has been removed.

Subtract the area of this square from the rectangle.

\(96 - 16 = 80~\text{cm}^2\)

Method 2

Break the shape into two squares and a rectangle.

Calculating the area of the compund shape using it's constituent shapes

Calculate the area of each shape.

\(4 \times 4 = 16~\text{cm}^2\), \(4 \times 4 = 16~\text{cm}^2\), \(4 \times 12 = 48~\text{cm}^2\)

Add the three areas together.

\(16 + 16 + 48 = 80~\text{cm}^2\)