1. Perimeter Section 9.2

2. Two measures of plane figures are important: a.the distance around a plane figure called the perimeter or circumference b.the number of square units in the interior of a plane figure called the area. and 2 Martin-Gay, Prealgebra, 5ed

3. llw w P  2l  2w Perimeter of a Rectangle Perimeter  2 length  2 width width length width length 3 Martin-Gay, Prealgebra, 5ed

4. Perimeter is always measured in units. Helpful Hint 4 Martin-Gay, Prealgebra, 5ed

5. s sss P  4s Perimeter of a Square Perimeter  4 side side 5 Martin-Gay, Prealgebra, 5ed

6. b a c P  a  b  cP  a  b  c Perimeter of a Triangle The perimeter of every polygon may be found by adding all the sides. a b c P  side a  side b  side c 6

7. The circumference is the distance around a circle. Circumference  diameter always results in the same ratio. This number is named “pi” and is approximately (  ) equal to or 3.14 7 22 diameter 7 Martin-Gay, Prealgebra, 5ed

8. Circumference of a Circle r d Circumference  2·   ·radius Circumference    ·diameter or C  2   r or C    d or 8 Martin-Gay, Prealgebra, 5ed

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