As an employee of the architectural firm of Brown and Farmer, you have been asked to design a silo to stand adjacent to an existing barn on the campus of the local community college. You are charged with finding the dimensions of the least expensive silo that meets the following specifications.

The silo will be made in the form of a right circular cylinder surmounted by a hemi-spherical dome.
It will stand on a circular concrete base that has a radius 1 foot larger than that of the cylinder.
The dome is to be made of galvanized sheet metal, the cylinder of pest-resistant lumber.
The cylindrical portion of the silo must hold 1000π cubic feet of grain.
Estimates for material and construction costs are as indicated in the diagram below.

The design of a silo with the estimates for the material and the construction costs.

The ultimate proportions of the silo will be determined by your computations. In order to provide the needed capacity, a relatively short silo would need to be fairly wide. A taller silo, on the other hand, could be rather narrow and still hold the necessary amount of grain. Thus there is an inverse relationship between r, the radius, and h, the height of the cylinder.


The construction cost for the concrete base is estimated at $20 per square foot. Again, if r is the radius of the cylinder, what would be the area of the circular base? Note that the base must have a radius that is 1 foot larger than that of the cylinder. Write an expression for the estimated cost of the base.


Surface area of base = ____________________

Cost of base = ____________________