For contractors and designers, adding and subtracting strings of dimensions is an everyday ritual. Some days it's an ordeal! So I've always thought, wouldn't it be great if you could add and subtract feet and inches on your regular calculator without converting inches to decimals? Well, you can. You don't need to be a math wizard or have a calculator with a bazillion functions, or even one of those expensive, complicated feet-inches calculators either. Quickly adding and subtracting dimensions on your basic, four-function calculator is easy to do. If you can remember a couple of simple rules and one easy Magic Number, you will be able to astound your friends and co-workers in about