Lesson 18 — Activity 3: Measuring the Area of a Triangle
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Lesson 18 — Activity 3:
Measuring
the Area of a Triangle
A triangle is half a parallelogram. Look at the shape to the left. You can see that there are two triangles that make up the parallelogram.
If you use the same formula as a parallelogram and take half of it, then you have the formula for the area of a triangle!
There are two formulas that you an use to find the area of a triangle.
They will both give you the same answer!
Where Area = base (b) x height 
÷ by 2.
Where A (Area) = 1/2 of the base (b) x the height .
Here is an example that shows how to find the area of a triangle.
You can also think of it this way:
Area = 50 mm x 30 mm ÷ 2
Area = 1,500 mm ÷ 2 = 750 mm squared
Area = 50 mm x 30 mm ÷ 2
Area = 1,500 mm ÷ 2 = 750 mm squared
Let's try another example!
Self-check!
Try This!
Try answering the questions below on your own first. When you have finished, click on the tab below to check your answers!
What is the area of a triangular sail that has a height of 12 feet and a base of 6 feet?
What is the area of a triangle that has a height of 8 feet and a base of 13 feet?
What is the area of a triangular sail that has a height of 12 feet and a base of 6 feet?
1/2 x 12 x 6 = 36 feet squared
What is the area of a triangle that has a height of 8 feet and a base of 13 feet?
1/2 x 8 x 13 = 52 feet squared