Optimization?

Question

A poster is to contain 102 square cm of printed matter, with margins of 5.5 cm each top and bottom and 2.5 on each of the sides. Find the minimal cost of the poster if it is to be made of material costing 12 cents per square cm.

Answer 1

Cost = 12 * L * W

(L - 11) * (W -5) = 105.

How you solve that depends on what class you're taking, but one way is to write L as a function of W based on the second equation, then differentiate cost with respect to W.