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Copyright © 3P Learning – These resources have been created in partnership with Dr. Marian Small.
For more information visit
www.mathletics.comTwo Triangles
Questions to facilitate the learning
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Did the tall triangle have to have any equal side lengths? Why or why not?
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Could the widths of the triangles have been similar? Why or why not?
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How could you create a triangle that is very wide with the same perimeter as the two you used?
Scaffolding the learning
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Suppose you chose a perimeter of 20 units. Could the tall triangle be 10 units high?
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What might its dimensions be?
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How could you make a less tall triangle with the same perimeter? What would you have to change about
the two triangles you created?
Extending the learning
Students might create shapes other than triangles with the same perimeter as the two triangles.
What’s the point of this task?
It is important for students to learn that shapes that look quite different can still have the same perimeter.
It helps students to think of taking a length and ‘bending’ it into a shape. Because one triangle is required
to be a lot taller than the other, the student is likely to use a number that is not too small as the perimeter.
Although neither triangle need be isosceles or equilateral, students tend to favour those kinds of triangles.
Questioning below will focus them on other types of triangles as well.
Measurement