Stage: 3 Challenge Level: 
All these triangles have a base of 1 unit and a height of 2 units. We could call them a "family" of triangles.
What are their areas? What do you notice?
Can you generalise to other "families" of triangles?
You may like to use the interactivity below to investigate more triangles
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Generalising. Interactivities. Visualising. Creating expressions/formulae. smartphone. Area. Games. Mixed triangles. Circles. Mathematical reasoning & proof.
Published May 2004.
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