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MHT CET202019 Oct 2020Morning ShiftMathematicsDifferential EquationsActual

If the radius of a circular blot of oil is increasing at the rate of 2 ~cm / min , then the rate of change of its area when its radius is 3 cms is

Options

  1. A10 cm ² / min
  2. B12 cm ² / min
  3. C14 cm ² / min
  4. D16 cm ² / min

Correct answer

B. 12 cm ² / min

Step-by-step solution

(A) Given dr dt =2 ~cm / min and r =3 cms Area = r² Differentiating w.r.t. t d A dt = 2 r dr dt = 2(3) (2)=12 cm ² / min

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