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Circles area


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Circles area

  1. 1. October 4, 2012 Circles2. The area of a circle. Next
  2. 2. Explanation October 4, 2012Here is a circle.You can divide it into sectors.The sectors can be rearranged, to form a shape veryclose to a rectangle.The two long edges are made up from the circumference,which is π × dOne side is made up from π × d ÷ 2 which is π × rEach of the short sides is made up from the radius.The area can now be calculated as π × r × r or π r ² π×r r More Next
  3. 3. Example October 4, 2012The second hand on a clock is 11cm long.What is the area of the clock face itpasses over in one minute? A = πr ² A = π × 11² A = π × 121 A = 380.1327…The area the second hand covers is is 380cm ² , to 3 s.f.In this case, it is sensible to give an answer to thenearest cm ². More Next
  4. 4. Example October 4, 2012A circular office carpet has a diameter of 1.8m.Calculate its area. A = πr ²Calculate the radius. r = 1.8 ÷ 2 = 0.9 A = π × 0.9 ² A = π × 0.81 A = 2.54690… The carpet is 2.54m² , to 2 d.p. It is sensible to give an answer to the nearest cm². More Next End