Area of Triangles: Using Base and Height

The area formula of a triangle is related to the area formula of a rectangle. Recall that the area of a rectangle can be determined by multiplying the length and width or the base and height.

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If the rectangle is cut in half, we know have a triangle. So the area would be half the area of the rectangle.

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Let's use the formula in some examples.

Ex. 1) Calculate the area of the triangle.

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Ex. 2) Calculate the area of the triangle.

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Ex. 3) Determine the area of the triangle.

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Ex. 4) The area of the triangle is 32 cm². Determine the height.

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To help visualize what this problem is asking, draw the other half so that it forms a rectangle.

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This rectangle would have an area of 64 cm².

A = bh

64 = 10(x)

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x = 6.4 cm

Let's review the steps.

Step 1: Double the area of the triangle. (This "undoes" the dividing by 2.)

Step 2: Divide the new area by the given side length.

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Ex. 5) The area of the triangle is 40 in². Determine the length of the height.

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Solution:

Remember, double the area and then divide by the known side length.

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Let's Review

To calculate the area of a triangle, we multiply the base times the height and divide by 2. If you are given the area, follow the steps backwards. You will multiply by 2 and divide by the given length.

Area of Triangles: Using Base and Height

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