Use the problem solving process to solve these problems. For this set of questions, after you identify the information you need, click on the link in the question or go to Information for Problem Solving Problems to find that information. The details may be imprecise; answer the question the best you can with the provided information. Document your steps and thinking.
I have an old gas furnace, and am considering replacing it with a new, high efficiency model. Is upgrading worth it? Information: Furnace Information
Lee et al., Math in Society, §1.5 Problem Solving, Exercise 28