Learning objects Area of triangles: triangles without vertical or horizontal sides


Find the area of triangles that do not have vertical or horizontal sides. Explore how the formula works. First, estimate the area of a chosen triangle on a grid. Next, work out the correct formula by assembling a series of triangles and rectangles. Then, compare the actual area of the triangle with your original estimate. Practise applying the formula directly to a range of triangles. This learning object is one in a series of four objects.

Educational details

Key learning objectives
  • Students estimate the area of triangles.
  • Students identify the base and height pairs of triangles.
  • Students identify the relationship between area of triangles and rectangles.
  • Students establish that all three base-height pairs can be used to calculate the area of triangles.
  • Students identify and apply the correct formula for calculating the area of a triangle.
Educational value
  • Provides a randomised range of triangle shapes on a square grid to help students estimate triangle areas.
  • Provides students with the choice of nominating the base and height pair of each triangle.
  • Demonstrates the link between the area of a triangle and the surrounding rectangle formed on the base via manipulation strategies, visual representations and equation forms.
  • Provides written clues and prompts to aid student progress as they practise finding the area of triangles using decimal lengths of the base and height.
  • Alerts students to the accuracy of their estimation.
Year level

7; 8

Learning area
  • mathematics
  • Mathematics/Measurement and geometry
    • Mathematics/Triangles
    • Mathematics/Area
    • Mathematics/Formulas
    • Analysis;
    • Application;
    • Comprehension;
    • Knowledge
    Student activity
    • Interactives;
    • Analysis;
    • Problem solving;
    • Modelling
    Learning design
    • Independent learning;
    • Problem solving;
    • Experiential learning

    Other details

    • Subject matter expert
    • Organisation: University of Western Sydney
    • Address: Penrith South NSW 2750 Australia
    • URL: http://www.uws.edu.au/
    • Technical implementer
    • Publisher
    • Date of contribution: 20 Sep 2013
    • Organisation: Education Services Australia
    • Address: Melbourne VIC 3000 Australia
    • URL: http://www.esa.edu.au/
    Access profile
    • Colour independence
    • Hearing independence
    Learning resource type
    • Interactive Resource
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    Operating systems
    • MacOS - minimum version: 10.6
    • MS-Windows - minimum version: XP - maximum version: 7
    • © Education Services Australia Ltd, 2013, except where indicated under Acknowledgements.