Maxima and minima problem A conical tent of the given capacity (volume) has to be constructed. Find the ratio of the
height to the radius of the base so as to minimise the canvas requried for the tent.

Write down expressions for the surface area and volume of the cone in terms of the radius of the base and the height. 
The problem gives you $volume=c$ for some given constant $c$. Solve this equation for height and substitute into the equation for surface area. This gives you surface area as a function of radius.
Now, you can take the derivative, set it equal to $0$ and apply the first/second derivative test to find a minimum. 
