What if you could tell if a stock is cheap without building a full discounted cash flow model? Like comparing the price per square foot of houses, you could use a few quick ratios to put a price tag on a company’s earnings, assets, or sales. In this chapter we walk through those workhorse multiples, uncover where they come from, and then tour the real‑world investment styles that put them to work — from classic value hunting to momentum riding and even tax‑smart portfolio tweaks.