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Chapter 12: Exponential Functions
Topic 3: Exponential Growth and Decay Classwork
Exponential Growth
1. Kaila received a $200 prize for her science fair project when she was in eighth grade. She choose to put
the money in a savings account to help pay for college. The account paid 4% annual interest. What is the
balance of the account 4 years later?
2. A movie theatre's matinee ticket price increases 4.5% every year. The price of a ticket is currently $3.50.
How much will it cost in ten years?
3. Patricia is the president of a software company. Every year her salary increases by the same percent as
sales. Sales increases 5% every year. If her starting salary is $30,000 a year, what will her salary be in
seven years?
4. A public library's membership increases 3% every year. In 1990, their membership was 275.
Approximately how many members will the library have in 2007? In 2017?
5. A savings certificate of $1,000 pays 6.5% annual interest compounded yearly. What is the balance after
the certificate matures in 5 years?
6. You deposited $1000 in a savings account that pays 5.5% annual interest compounded yearly. What is
the balance after three years and nine months?
Exponential Decay
1. You bought a used boat for $42,000. The value of the boat will decrease each year because of
depreciation. The boat depreciates at the rate of 7.5% per year. Find the value of the boat after 6 years.
2. You bought a used car for $18,000. The value of the car will be less each year because of depreciation.
The car depreciates at the rate of 12.08% per year. Estimate the value of your car in 8 years.
3. Greg has $200,000. He decides to invest his money into a stock portfolio which ends up losing an average
of 4% interest annually. What is the balance after 5 years?
4. You bought a used truck for $2,300. It depreciates at a rate of 8.2% a year. What is the worth of the truck
after 3.5 years?
5. A summer youth camp had a declining enrollment from 1995 to 2000. The enrollment in 1995 was 320
people. Each year for the next five years, the enrollment for each year decreased by 2%. Make a chart
showing the enrollment since 1995 until 2000.
6. The number of bacteria that grow in a gel plate is approximated by the function
, where t
is time in minutes, with t = 0 corresponding to the starting time. Use this model to approximate the
number of bacteria present after t minutes when t equals
(a) 0 minutes
(b) 5 minutes
(c) 15 minutes
(d) 20 minutes