Question -
Answer -
The area of a circle (A)with radius (r) isgiven by,
Now, the rate of change ofthe area with respect to its radius is given by,
When r = 3 cm,
Hence, the area of the circle is changing at the rate of6Ï€ cm when its radius is 3 cm.
When r = 4 cm,
Hence, the area of the circle is changing at the rate of8Ï€ cm when its radius is 4 cm.