Question

The radius of a circle is a increasing at the ratio of 0.4 cm/s.the rate of increase of its circumsference is :

Answer 1

Answer:

$0.8\pi cm/s$

Step-by-step explanation:

We are given that

Rate at which radius of circle increases=0.4 cm/s

We have to find the rate of increase of its circumference.

We know that

Circumference of circle,C=$2\pi r$

Differentiate w.r.t times

$\frac{dC}{dt}=2\pi \frac{dr}{dt}$

Substitute the value

Then, we get

$\frac{dC}{dt}=2\pi (0.4)=0.8 \pi cm/s$

Hence, the rate at which circumference of circle increasing=$0.8\pi cm/s$