Modeling Exponential Functions Percent Growth Decay

Marilyn collects old dolls. She purchases a doll for $450. Research shows this doll's value will increase by 2.5% each year. Write an equation that determines the value, V, of the doll t years after purchase.

• V = 450(1 + 0.025)^t

• V = 450(1 – 0.025)^t

• V = 450(1 + 2.5)^t

• V = 450(1 – 2.5)^t

A car was purchased for $25,000. Research shows that the car has an average yearly depreciation rate of 18.5%. Create a function that will determine the value, V(t), of the car t years after purchase.

• V(t) = 25000(1 – 0.185)^t

• V(t) = 25000(1 + 0.185)^t

• V(t) = 25000(1 – 18.5)^t

• V(t) = 25000(1 + 18.5)^t

The population of a town is currently 6342 and is increasing by a rate of 1.3% each year. Which function represents the population of people, P, after t years.

• P = 6342(1 + 1.3)^t

• P = 6342(1 – 1.3)^t

• P = 6342(1 + .013)^t

• P = 6342(1 – .013)^t

An antibiotic is introduced into a colony of 12,000 bacteria during a laboratory experiment. The colony is decreasing by 15% per minute. Which function can be used to model the number of bacteria in the colony after x minutes?

• f(x) = 12000(1.15)^x

• f(x) = 12000(0.15)^x

• f(x) = 12000(0.85)^x

• f(x) = 12000(1.85)^x

The bear population in a given area is currently 1580. They anticipate the bear population to decrease by 2% each year. Which function represents the population of bears, B, after t years.

• B = 1580(0.02)^t

• B = 1580(1 – 0.02)^t

• B = 1580(1 + 0.02)^t

• B = 1580(1 – 0.2)^t

The value of a car is $15,000 and depreciates at a rate of 8% per year. What is the exponential equation?

• y=8(15,000)^x

• y=15,000(0.92)^x

• y=15,000(1.08)^x

• y=15,000(0.08)^x

What function is present? 

• Absolute Value

• Exponential Decay

• Linear Equation

• Exponential Growth

A student invests $500 for x years in a savings account that earns 4% interest per year. No further deposits or withdrawals are made during this time. Write an function f(x) to represent the amount of money earned after x years.

• f(x) = 500 (.60)^x

• f(x) = 500 (.96)^x

• f(x) = 500 (1.04)^x

• f(x) = 500 (1.4)^x

Rhonda deposited $3000 in an account in the Merrick National Bank, earning 4.2% interest, compounded annually. She made no deposits or withdrawals. Write an equation that can be used to find B, her account balance after t years.

• B = 3000(1 – 4.2)^t

• B = 3000(1 + 4.2)^t

• B = 3000(1 – 0.042)^t

• B = 3000(1 + 0.042)^t

Which of the following functions shows an initial amount of $15 and an increase of 35% each year?

• y = 15(1.035)^x

• y = 15(1.35)^x

• y = 15(0.35)^x

• y = 15(0.65)^x