Q:

calculus how fast is the milk's level rising at 3 seconds?

Suppose milk is being poured into a cylindrical bowl of radius 5 inches at a rate of 1 cubic inch per second. How fast is the milk's level rising at 3 seconds?

A:

Let V be the volume of the cylinder that is filled with milk.
Clearly $\frac {dV}{dt}$ will give you the rate of change of volume with time.
$$V=2\pi r^2h$$ where r is the radius and h is the height.
$$\frac {dV}{dt}=4\pi r\frac{dh}{dt}$$
$${\frac {dV}{dt}}_{t=3}=4\pi r({\frac{dh}{dt}}_{t=3})$$
will give you how fast the volume is changing at time t=3s

