Water runs into a conical tank of radius $5$ ft and height $10$ ft at a constant rate of
$2\text{ ft}^3/\text{min}$.
How fast is the water level rising when the water is $6$ ft deep?
The rate of increase of length of the shadow of a man $2$ meters high, due to a lamp at $10$ meters height, when he is moving away from it at $2 \text{ m/sec}$ is