2. Circles: Circumference & Area Tutorial 8c A farmer might need to find the area of his circular field to calculate irrigation costs.

3. Circumference Circumference is the distance around a circle. Similar to the perimeter of a polygon. The circumference of a circle is slightly more than three times the length of its diameter (actually 3.1415...)

4. Circumference The number 3.1415... Goes on forever without repeating. We have come to refer to this number as pi (  ). It is represented by the Greek symbol . As a fraction,  is approximately 22/7. As a decimal,  is approximately 3.14.

5. Circumference To find the circumference of a circle we use one of the following formulas. Circumference(c) =  times the diameter(d) C =  d Or since the diameter is twice the radius- C = 2  r Diameter

6. Example #1 Find the approximate circumference if the diameter has a length of 5 inches. Diameter 5” C =  d =  5  (3.14) 5  15.7 The circumference is approximately(  ) 15.7 inches

7. Area of a circle The formula to find the area of a circle is pi (  ) times the radius (r) squared. A =  r 2 Diameter 14” Example: Since the diameter is 14, the radius must be 7. A =  r 2 =  7 2 =  7 7 = (3.14) 49 = 153.86 square feet