Adding-And-Subtracting-Areas Wjec-Eduqas Higher

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Exam code:C300

Adding & subtracting areas

What is a compound shape?

Sometimes you will have a shape that is not a standard shape such as a rectangle, triangle, trapezium etc.
- These are often called compound shapes
- We can split the non-standard shape into standard shapes

How do I find the area of a compound shape?

Split the compound shape into standard shapes
Find the areas of the standard shapes
Add these areas together to find the area of the compound shape
Occasionally it may be easier to add an extra shape to the diagram and subtract the area of the extra shape from the new bigger shape
- For the shape below you might complete the rectangle by putting a triangle in the top right corner
- The area of the original shape is the rectangle minus the triangle

Examiner Tips and Tricks

Take a moment to think about how to split up the shape into the easiest shapes possible – there will probably be more than one way to do it!

Worked Example

Find the area of the pentagon shown in the diagram below.

Pukoyl43_edexcel-3-5-2-adding-and-subtracting-areas-we-diagram

Separate the diagram into two shapes that you are familiar with and know the area formulae for
This pentagon can easily be split into a rectangle and a triangle

Use the values given to find the length of the base and the height of the triangle and add these to the diagram.

A compound shape split into standard shapes

The total area will be the area of the rectangle + the area of the triangle.

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