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Thursday, November 22, 2012

Perimeter


A square and an equilateral triangle are both examples of regular polygons. Another method for finding the perimeter of a regular polygon is to multiply the number of sides by the length of one side. Let's revisit Examples 3 and 4 using this second method.

Example 3:Find the perimeter of a square with each side measuring 2 inches.[IMAGE]
Solution:This regular polygon has 4 sides, each with a length of 2 inches. Thus we get:
 P = 4(2 in) = 8 in

Example 4:Find the perimeter of an equilateral triangle with each side measuring 4 centimeters.[IMAGE]
Solution:This regular polygon has 3 sides, each with a length of 4 centimeters. Thus we get:
 P = 3(4 cm) = 12 cm

Example 5:Find the perimeter of a regular pentagon with each side measuring 3 inches.[IMAGE]
Solution:P = 5(3 in) = 15 in

Example 6:The perimeter of a regular hexagon is 18 centimeters. How long is one side?[IMAGE]
Solution:P = 18 cm
 Let s represent the length of one side. A regular hexagon has 6 sides, so we can divide the perimeter by 6 to get the length of one side (s).
 s = 18 cm ÷ 6
 s = 3 cm

Summary:To find the perimeter of a polygon, take the sum of the length of each side. The formula for perimeter of a rectangle is: P = 2L + 2W. To find the perimeter of a regular polygon, multiply the number of sides by the length of one side.

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