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# Area of triangles: triangles with a right angle

TLF ID L354

Find the area of right-angled triangles. 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 right-angled 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 right-angled triangles, including the base-height pair formed by the perpendicular sides of the triangle.
• 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 right 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 right triangles.
• Alerts students to the accuracy of their estimation.
Year level

7; 8

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

#### Other details

Contributors
• 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
Browsers
• Microsoft Internet Explorer - minimum version: 8.0 (MS-Windows) - maximum version: 9.0 (MS-Windows)
• Firefox - minimum version: (MS-Windows)
• Safari - minimum version: 5.1 (MacOS)
Operating systems
• MacOS - minimum version: 10.6
• MS-Windows - minimum version: XP - maximum version: 7
Rights
• © Education Services Australia Ltd, 2013, except where indicated under Acknowledgements.