This chapter will emphasize the method of computing simple interest. It first introduces the basic concepts and operations of simple interest (Sections 0.0 and 0.0) and simple discount (Section 0.0). These basic topics are essential for understanding the material presented in the following chapters, such as bank discount, compound interest, annuities, and life insurance premiums. Next, this chapter illustrates the general applications of the simple interest and simple discount methods for debt payments (Sections 0.0 to 0.0). It concludes with a summary of the simple interest formulas (Section 0.0).