Technomaths

Composite shapes

June 2, 2011

composite shape

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Learning Intention:  Understand that the area of all composite shapes can be calculated by breaking the shape down into known areas.

Success Criteria: You will be able to summarize the formulae to calculate the area of the following 2 dimensional shapes and break down a composite shape by identifying each of the known shapes and correctly calculating their area.

  • squares and rectangles
  • triangles
  • parallelograms
  • trapeziums
  • circles and annuli

Some examples of these kinds of problems are in Exercise 8G (page 326) of MathsQuest8. Here are some other activities to learn about the area of composite shapes.

  • An L-shaped room has a perimeter of 20m. What might the area of the floor be?
  • The difference in areas of two rectangles is 32cm (squared). What might the widths and lengths of the two rectangles be?

Your homework (due Friday) is one of the following:

  • Use Google Maps or Google Earth to find an aerial view of an unusual shape, take a screen shot and calculate it’s area using the scale measurements. Copy your screen shot into “Paint”, add the measurements, calculate the area and email it to me. You may choose a large building, carpark or arena (the MCG or Etihad stadium for example) or perhaps your farm or property.
  • Use a stencil or simple font to write the initials of your name,  and calculate the area of the letters. Make sure you email me a copy of your calculations, or leave a comment below about your task.


  1.   Robin Kine says :

    Composite shapes are made of basic planner (2D) shapes. If students know how to find the area of such 2D shapes such as rectangles, triangles and circles then they can evaluate the area of complex shapes, as explained in the above presentation.

    Beautifully explained presentation about finding the area of composite shapes. Well defined images.

  2.   brittgow says :

    Thanks for your comment Robin. Students sent me some great images of aerial photographs of their farms and homes with the area calculated. This was an interesting activity to assess their understanding of the work we have done before and of composite shapes.

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