Refer to the following in doing Exercises 73–75. In the savings formula, the interest rate appears twice. The particular ways in which is involved make it impossible to solve it algebraically to get an explicit formula for . However, with the help of a spreadsheet, you can find approximately when the other quantities are given.
74. (Spreadsheet helpful) A 1990 advertisement read, “If you had put $100 per month into this fund starting in 1980, you’d have $37,747 today.” Assume that deposits were made on the last day of the month, starting in January 1980, through December 1989, and that interest was paid monthly on the last day of the month (120 months).