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Math and Arithmetic

How do you find a perimeter?


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April 17, 2011 9:04PM

Finding the perimeter of a geometric figure involves calculating the distance around that figure. It's as simple (or as difficult) as that. Let's look further.

As you may have guessed, the shape of the figure will dictate the approach used. For any three- or more-sided figure, the perimeter can be found by adding up the lengths of all the sides. If the sides of all of equal length, as in an equilateral triangle, a square, or any regular polygon, multiply the length of one side by the number of sides. That seems pretty intuitive, or even simple, but it is important to state it. There are other figures that require more work or a different approach.

An irregular triangle, quadrilateral or polygon asks the investigator to add up the lengths of all the sides after measuring or calculating each of their lengths. For circles, the perimeter is a matter of finding the circumference, which is pi times the diameter (or pi times two times the radius, which is the same thing). Other geometric shapes require more intensive work. An ellipse is a shape that asks more of the individual finding a perimeter, but the basics are set down here.