ALGEBRA II EXPO STORY PROBLEMS
1. The amount of fuel used annually by each car in the US has decreased by about 2% each year
since 1980, when it was about 591 gallons.
a) Write an exponential function to model this situation.
b) Estimate the average number of gallons of gasoline used by a car in 1987.
2. The population in Wisconsin was about 4.7 million in 1980 and about 4.9 million in 1990.
a) Write an exponential function to model the population of Wisconsin over time.
(Find the growth rate PER DECADE.)
b) Use the model you wrote to estimate the population in 1970.
3. Peter Griffin puts aside $350 a month for Stewie’s college fund. After a year and a half, he
moves the money to Quahog National. They offer him two options:
a) 4.32% interest compounded continuously
b) 5.12% compounded semi annually (use the formula on page 444 under ‘Problem Solving Hint’).
After 16 years, which option leaves him with more money?
4) According to the US Census Bureau, the population of Colorado in the year 1990 was
3,294,394. The population of Colorado in the year 2000 was 4,301,261. Write an exponential
equation in the form y  ab x to model the population of Colorado since 1990.
5) Use your equation from question 4) to predict the population of Colorado in the year:
a. 2050
b. 1950
6) Dasher is looking towards retirement. Santa gave him his quarterly bonus of $2,500. The
North Pole Bank will give him an interest rate of 3.5%. The South Pole Credit Union will give
him 3.12% compounded continuously. Where should Dasher look to put his money…
If he can retire is 5 years?
In 20 years?
7) I-123 is used in thyroid scans. It has a half life of 13.2 hours. Write the exponential decay
function for a 45mg sample. Find the amount remaining after 5 hours.