A triangle is defined as a closed figure with three sides. The length of all three sides of a triangle added together is called the perimeter. You can calculate the perimeter (P) of a triangle using addition if you know the lengths of each side (a, b and c). The formula for calculating the perimeter of a triangle is therefore P = a + b + c.
Instructions
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1
Measure each side of the triangle. Label each side of the triangle with that side's measurement.
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2
Add the lengths of the three sides. Add side a, plus side b, plus side c.
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3
The sum of the three sides is the perimeter of, or length around, the triangle.