Topic 9 Review: Exponential Functions

Question 1: An electronic keyboard depreciated in value by a fixed percent per year. The value, y, is modeled in the graph, where x represents the number of years since the keyboard was manufactured.

Based on the graph, which statement does not appear to be

true?

• A The keyboard originally cost $3,000.

• B The keyboard decreases by $500 each year.

• C After 3 years, the keyboard lost half its value.

• D After 5 years, the value of the keyboard was $1000.

Question 2: A population of 3000 penguins increases by 7.1% per year. Approximately how long will it take for the penguin population to be more than double the current population?

• A. 10 years

• B. 14 years

• C. 17 years

• D. 20 years

Question 3: A particular type of cell doubles in number every hour. Which function can be used to find the number of cells present at the end of h hours if there are initially 4 of these cells?

• A. n = 4(1/2)^h

• B. n = 4(2)^h

• C. n = 4 + 2^h

• D. n = 4 + (1/2)^h

Question 4: A student used to show how the balance in a savings account will increase over time. What does the 5.00 represent?

• A. The interest the savings account earned for the first year.

• B. The annual interest rate of the savings account.

• C. The number of years the savings account has earned interest.

• D. The starting balance of the savings account.

Question 5: The amount of fertilizer in a landscaping company’s warehouse decreases at a rate of 3% per week. The amount of fertilizer in the warehouse was originally 78,000 cubic yards. Which function models the amount of fertilizer in cubic yards left after w weeks?

• f(w) = 0.97(78,000)^w

• f(w) = 1.03(78,000)^w

• f(w) =78,000(0.97)^w

• f(w) = 78,000(1.03)^w

Question 6: A table of values for the exponential function f is shown below.

Which situation could describe this function?

• A. The value of a house increases by approximately 2 3/4% per year.

• B. The value of a house increases by $3,850 per year.

• C. The value of a house decreases by approximately 2 3/4% per year.

• D. The value of a house decreases by $3,850 per year.

Question 7: A student put $1,500 in a savings account that paid 3% interest compounded annually. The function that models the value of the account, y, after t years is shown below. What is the missing value?

• 103

• .97

• .03

• 1.03

Question 8: The initial value of an exponential function is 1.8. The rate of growth is 4.2% Which equation models the value of this function, y, over time t?

• A. y = 1.8(1.42)^t

• B. y = 1.8 + 4.2^t

• C. y = 1.8(1.042)^t

• D. y = 1.8(4.2)^t

Question 9: The number of wolves in a wildlife refuge can be modeled by an exponential function, where x is the number of decades since population counts began, and y is the average annual number of wolves during the decade. The data for three decades is given in the table.

Which graph is a graph of the function?

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• 
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Question 10: The table gives the bids for a rare book at an online auction, where x is the number of the bid and y is the amount in dollars. The bids increased exponentially.

Which function models the values of the bids?

• A. y = 240(1.25)^x

• B. y = 200(1.5)^x

• C. y = 168.75(1.25)^x

• D. y = 240(1.5)^x