Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways

You can decompose or split shapes into rectangles in different ways.

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Year 5

Calculate the area of shapes made from 2 rectangles by decomposing the shape in different ways

You can decompose or split shapes into rectangles in different ways.

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Share activities with pupils

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Lesson details

Key learning points

Different ways of decomposing the shape will give the same answer.
The area stays the same however you split the shape.
Calculate the areas of the rectangular parts and recombine to find the area of the whole shape.

Keywords

Rectilinear - A shape made up of two or more rectangles is known as rectilinear.
Compound - A compound shape is one made up of two or more shapes.

Common misconception

Some pupils may not see that two rectilinear shapes can look very different but have the same area.

Cut out a large rectangle. Cut it into two rectangles. Ask pupils to move one of the rectangles and reposition it. Has the area changed?

Some pupils may need extra practice with working out the area of compound shapes where the rectangles are not pre-marked before they move onto example requiring them to divide the shape into rectangles.

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).