InterviewSolution
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The areas of two circles differ by 100 cm2 andtheir circumterence differ by 10 cm, what isthe sum of their radi i ? |
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Answer» Let a large circle with the radius of "a" and the radius of the smaller circle be "b", As given in the question, ⇒ Difference of areas = 100 cm^2 ⇒ Area of large circle - Area of small circle = 100 cm^2 From the properties of circle, we know : - Area of circle = πr^2, where r is the radius of the circle = > πa^2 - πb^2 = 100 cm^2 = > π( a^2 - b^2 ) = 100 cm^2 Also, ⇒ Difference of their perimeter = 10 cm ⇒ Perimeter of large circle - perimeter of small circle = 10 cm From the properties of circle, we know : - Perimeter of circle = 2πr= > 2πa - 2πb = 10 cm = > 2π( a - b ) = 10 cm Now,= > π( a^2 - b^2 ) = 100 cm^2 --- ( 1 ) = > 2π( a - b ) = 10 cm --- ( 2 ) Divide ( 1 ) by ( 2 ), we get a + b = 20 cm Now,= > 2π( a - b ) = 10 cm = > a - b = 10 cm x 1 / 2 x 7 / 22 = > a - b = 35 / 22 cm Then, adding a + b and a - b,a + b = 20 cma - b = 35 / 22 cm 2a = 20 + 35 / 22 cm = > 2a = ( 440 + 35 ) / 22 cm= > 2a = 475 / 22 cm= > a = 475 / 44 cm And, a + b = 20 cm b = 20 cm - 475 / 44 cm b = 405 / 44 cm Hence, radius of larger circle is 475 / 44 cm and radius of smaller circle is 405 / 44 cm. |
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