How do I work out the area of a right angled triangle?

If we think about a right angled triangle, it is the same as one half of a square or rectangle. This is because if we join two right angled triangles at their diagonal sides, we make a square or rectangle.

Now, in order to work out the area of a square or rectangle, we simply multiply the length and the width together.

However, we now have the area of a square or rectangle, when we actually need the area of the right angled triangle. To work out the area of the roght angled triangle, we must simply halve the area that we have worked out. This is because we have made the square or rectangle by putting 2 right angled triangles together. As there are 2 of them, we must simply divide the whole area by 2 in order to find the area of one right angled triangle.

This is why we say that in order to work out the area of a right angled triangle we simply do:

Length x Width and then divide the answer by 2

Ciaran C. 11 Plus Maths tutor, 11 Plus English tutor

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