Quiz Review: Applications of Exponential Functions A high school senior has saved $15,000 from birthdays, summer jobs and graduation gifts throughout the past several years. They decide to invest the money. They find a CD that has an annual rate of 10%. Use Excel to help you complete the following tables: SIMPLE INTEREST Time (years) Interest COMPOUND INTEREST Present Value 1 2 3 4 5 6 7 8 9 10 Use Excel to plot a graph of Present Value vs. Time for Simple Interest. Paste your graph below. Simple interest grows at a ____________ rate. Time (years) Principal Interest Present Value 1 2 3 4 5 6 7 8 9 10 Use Excel to plot a graph of Present Value vs. Time for Compound Interest. Paste your graph below. Compound Interest grows at an __________________ rate. Quiz Review: Applications of Exponential Functions Question #2 A grandparent invests $8,000 in a U.S. savings bond for their grandchild’s retirement when their grandchild is first born. The receive a rate of 9% interest on their savings bond. The interest is compounded annually. They specify that their grandchild is not allowed to cash in the savings bond until the age of 65 at their retirement. Use Excel to determine how much the savings bond will be worth when the grandchild cashes it in. Question #3 Cell Phone Subscribers The table below gives the number y (in millions) of cell-phone subscribers from 1988-1997 where t is the number of years since 1987. t 1 2 3 4 5 6 7 8 9 10 y 1.6 2.7 4.4 6.4 8.9 13.1 19.3 28.2 38.2 48.7 a.) Use your calculator to plot y vs. t. What type of model would best fit the data? b.) Use the exponential regression feature of your graphing calculator to find a model for the data. c.) What is the r2 value for the regression model in b? d.) Use the model to estimate the number of cell-phone subscribers in 1998.