Simple Exponential Growth and Decay Models

Classify the model as Exponential GROWTH or DECAY.
A=10(1.01)³

• Growth

• Decay

A population of fish starts at 8,000 and decreases by 6% per year. What is the population of fish after 10 years?

• 14327

• 4309

• 839

• 7680

Steve deposited

$5,000 in a savings account that pays 4% interest compounded annually. Which

equation could be used to find the value of the account after 3 years?

• A = 5,000(1 + 4)³

• A = 5,000(1 + 0.04)³

• A = 5,000(1 + 0.4) x 3

• A = 5,000(0.04)³

The amount of ants in a colony, f, that is decaying can be modeled by                         f(x) = 800(.87)^x, where x is the number of days since the decay started. Suppose           f(20) = 49. Which of the following is true?

• After 20 days, there are 49 ants in the colony.

• After 49 days there are 20 ants in the colony.

• The amount of ants times 20 is 49.

• After 20 days the amount of ants remaining decreases by 49.

The expression 12(1.015)^t models the population of elephants in a wildlife refuge after t years since 1975.
What does the value 1.015 represent?

• The number of elephants was 1,015 in 1975.

• The number of elephants increases by 1.5% each year.

• The number of elephants increases by 101.5% each year.

• The number of elephants is multiplied by 1.015 each year.

Is the following function exponential growth, exponential decay, linear, or none of the above.
g(x) = 740(.001)^3x

• Exponential growth

• Exponential decay

• Linear

• None of the above

Suppose a culture of bacteria begins with 5000 cells and dies by 30% each year. Write an equation that represents this situation.

• y=5000(0.7)^x

• y=30(5000)^x

• y=5000(1.3)^x

• y=5000x^x

Is this exponential growth or decay?

• Growth

• Decay

What is the pattern you see in this table?

• Common Ratio = 1/3

• Common Difference = 8

• Common Ratio = 3

• Common difference = 3

Pick the equation that is exponential decay

• y=2000(0.88)

• y=0.5(1.88)