# Area of triangles: height intersects with the base inside the triangle

TLF ID L355

Find the area of triangles that have vertical or horizontal sides. In this type of triangle, the height intersects with the base inside the triangle. Explore how the formula for finding the area of a triangle 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.
• Encourages students to nominate a vertical or horizontal side as the base.
• Demonstrates the link between the area of a triangle and its surrounding rectangle formed on the triangle 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 base and height lengths found on the grid.
• 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
• Technical implementer
• Subject matter expert
• Organisation: University of Western Sydney
• Address: Penrith South NSW 2750 Australia
• 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.

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