The “Rate of Return” method is one of the most popular methods used in business for the assessment of the economic worth of revenue investments. However, most introductory finance texts lack rigorous mathematical treatment of the subject, have different treatments for the case of multiple values, and present some facts with ambiguity. In this paper, we shall try to give more solid definitions and prove some new and known facts about the method. We will develop an easier alternative method in the special case of mutually exclusive simple investments that avoids the use of incremental analysis.