The radius of a circle is increasing at the rate of 0.7 cm/s. What is

1.	The radius of a circle is increasing at the rate of 0.7 cm/s. What is the rate of increase of its circumference?
Answer» Consider the radius of the circle as r dr/dt = 0.7 cm/s We know that circumference of the circle = 2πr So the rate of change of circumference = 2π dr/dt By substituting the values we get = 2 × 3.14 × 0.7 We get dC/dt = 4.4 cm/s

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

Answer»

Consider the radius of the circle as r

dr/dt = 0.7 cm/s

We know that circumference of the circle = 2πr

So the rate of change of circumference = 2π dr/dt

By substituting the values we get

= 2 × 3.14 × 0.7

We get

dC/dt = 4.4 cm/s