# Quiz Review: Applications of Exponential Functions

```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
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.
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.
```