# Exponential Growth And Decay Word Problems

Unit 3
Name: ____________________ Pd:_____
Exponential Growth and Decay Word Problems
1. Find a bank account balance if the account starts with \$100, has an annual rate of 4%, and the money left
in the account for 12 years.
2. In 1985, there were 285 cell phone subscribers in the small town of Centerville. The number of
subscribers increased by 75% per year after 1985. How many cell phone subscribers were in Centerville in
1994?
3. Bacteria can multiply at an alarming rate when each bacteria splits into two new cells, thus doubling. If we
start with only one bacteria which can double every hour, how many bacteria will we have by the end of
one day?
4. Each year the local country club sponsors a tennis tournament. Play starts with 128 participants. During
each round, half of the players are eliminated. How many players remain after 5 rounds?
t
5. The population of Winnemucca, Nevada, can be modeled by P=6191(1.04)
where t is the number of years
since 1990. What was the population in 1990? By what percent did the population increase by each year?
6. You have inherited land that was purchased for \$30,000 in 1960. The value of the land increased by
approximately 5% per year. What is the approximate value of the land in the year 2011?
7. During normal breathing, about 12% of the air in the lungs is replaced after one breath. Write an
exponential decay model for the amount of the original air left in the lungs if the initial amount of air in
the lungs is 500 mL. How much of the original air is present after 240 breaths?