Q3 of 168 Page 197

The radius of a circle is increasing uniformly at the rate of 3 cm/s. Find the rate at which the area of the circle is increasing when the radius is 10 cm.

We know that area of a circle (A) is A = πr2

Then, Rate of change of the area with respect to time is given by,



It is given that



Then,


Thus, when r = 10cm


Then


Therefore, the rate at which the area of the circle is increasing when the radius is 10 cm is 60π cm2/s.


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