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 Perimeter, Part II Unit 1 > Lesson 1 of 8

 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. Solution: This regular polygon has 4 sides, each with a length of 2 inches. Thus we get: = 4(2 in) = 8 in Example 4: Find the perimeter of an equilateral triangle with each side measuring 4 centimeters. Solution: This regular polygon has 3 sides, each with a length of 4 centimeters. Thus we get: = 3(4 cm) = 12 cm Example 5: Find the perimeter of a regular pentagon with each side measuring 3 inches. Solution: = 5(3 in) = 15 in Example 6: The perimeter of a regular hexagon is 18 centimeters. How long is one side? Solution: = 18 cm Let 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 (). = 18 cm ÷ 6 = 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: . To find the perimeter of a regular polygon, multiply the number of sides by the length of one side.