Q1 of 30 Page 6

Find the rate of change of the area of a circle per second with respect to its radius r when r = 5cm.

Note: we cannot calculate change per second because nothing is given about that is change of radius with respect to time


Area of circle (A) having radius r is given by A = πr2


Differentiate A with respect to r



As we have to find the rate of change when r = 5 cm put r = 5 cm




Hence the change in area with respect to radius is 10π cm2/cm


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