If the radius of a circle changes at the rate of `0. 2 cm//sec`, then , when the radius is 20 cm, its area changes at the rate of

If the circumference of a circle changes at rate of 0.2 cm //sec , then , when the radius is 8 cm , its area is changing at the rate of

If the circumference of a circle at the rate of 0.2 cm //sec , then, when the radius is 8cm, its area is changing at the rate of

If the area of a circle change at the rate of 0.8 cm^(2)//sec , then, when the radius is 4 cm , it circumference changes at the rate of

If the area of a circle changes at the rate of 2pi cm^(2)//sec , then, when the radius is 10cm, the radius is changing at the rate of

If the circumference of a circle changes at the rate of 0.7 pi cm //sec , then, when the radius is 5 cm, the radius is changing at the of

If the volume of sphere changes at the rate of 140 cm^(3)//sec, then, when the radius is 70 cm, its surface area is increasing at the rate of

If the radius of the circle changes at the rate of 0.04 cm//sec , then the rate of change of its area, when radius is 10 cm, is

If the radius of a circle is increasing at the rate of 2 cm/ sec, then the area of the circle when its radius is 20 cm is increasing at the rate of

If the radius of a circle is 2 cm and is increasing at the rate of 0.5 cm/sec., then the rate of increase of its area is