Calculating Area – Triangles

Lesson Summary:

The lesson shows the children how to measure the area of triangle.  The discussion is designed to be read by the children. Activity A requires them to work out the area of a triangle when provided with the base and the height. Activity B gives them the opportunity to draw, measure and calculate the areas of their own triangles: right, acute and obtuse.


  • The children will be understand and be able to demonstrate how the area of a triangle is calculated.

Subject Area:


Lesson Excerpt:

Do you remember how to calculate the area of a square or rectangle? Both of these shapes are parallelograms.  The method you use the calculate the area of a parallelogram is to multiply the base by the height, and the answer will give you the area in square units.  This is what the formula looks like: A = b x h   (A is area, b is base and h is height.)

Now let’s look at triangles: How do we find the area of a triangle?  Well, it helps to remember that a triangle is half of a parallelogram:

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