The diameter of a circle is increasing at the rate of 1 cm/sec. When its radius is `pi`, the rate of increase of its area, is

The radius of a circle is increasing at the rate of 0.7 cm/sec. What is the rate of increase of its circumference?

The radius of a circle is increasing at the rate of 0.7 cm/sec. What is the rate of increase of its circumference?

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

The radius of a soap bubble is increasing at the rate of 0.2 cm/sec. It its radius is 5 cm, find the rate of increase of its volume.