# [SOLVED]Volume rate of change

#### karush

##### Well-known member
View attachment 1561

on b) I think this is the point they wanted us to get
hope answers are correct its an even problem # so no ans in bk.

#### MarkFL

In your working, where you evaluate $$\displaystyle \frac{dV}{dt}$$ for the given values of $r$, you should have replaced $$\displaystyle \frac{dr}{dt}$$ with $$\displaystyle 3\,\frac{\text{in}}{\text{min}}$$ instead of $$\displaystyle 3\text{ in}$$. Also, I think what they are looking for in part b) is that $$\displaystyle \frac{dV}{dt}$$ is proportional to the square of $r$. Thus it changes quadratically, not exponentially.