I simply cannot do these problems. Putting them into some sort of workable function escapes me completely.
A rectangular storage container with an open top is to have a volume of 10 cubic meters. The length of its base is twice the width. Material for the base costs $13 per square meter. Material for the sides costs $10 per square meter. Find the cost of the materials for the cheaptest such container. Round the result to the nearest cent.
That ^ for instance. How would you even begin to approach it?