Activities for Students: Seeing How Money Grows
Compound interest is very much a part of the life of every student. Albert Einstein once called the compound interest formula the most important formula in mathematics. Unfortunately, many students never see the formula unless they take enough mathematics to encounter it in their study of exponential functions. Even then, they may experience it only algebraically, not graphically. Its predecessor, the simple interest formula, is usually studied in isolation, often in a “consumer math” application as an exercise in arithmetic or perhaps in algebra. Few students realize that the simple interest formula can be modeled with the graph of a linear equation when the principal and interest rate are held constant. In a similar way, the compound interest formula can be modeled graphically as an exponential curve. Any student who can make tables and plot points can graph the future value of an account using simple and compound interest and can thereby come to appreciate the meaning of the variables in each formula and how those variables contribute to the growth of an account.