Exponential functions

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. By what percentage is the colony decaying?

• 87%
• 13%
• 800%
• 8.7%

Which of the following is an increasing exponential function whose y-intercept is 50?

• y = 50(.05)^x
• y = 50x - 4
• y = (2)^x + 50
• y = 50(1.4)^x

The expression 12(1.015)^t models the population of elephants in a wildlife refuge after t years since 1975.
Is the population of elephants increasing or decreasing?

• Increasing
• Decreasing

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

• The predicted increase in number of elephants in the refuge each year.
• The predicted decrease in number of elephants in the refuge each year.
• The number of years it will take for the elephant population to stop increasing.
• The initial amount of elephants in the park.

Identify the y-intercept (initial value) in the function f(x)=13(.27)^x

• (.27)^x
• .27
• 13
• 3.51

Is the following function and example of decay or growth?

f(x)=2(0.85)^x

• Exponential Decay

• Exponential Growth

Is the following function an example of decay or growth?

f(x) = 2(1.25)^x

• Exponential Growth

• Exponential Decay

Classify the function, f(x) = 6.5(0.85)^x.

• exponential growth
• exponential decay
• positive linear
• negative linear

A liquid is evaporating. The amount of a liquid remaining, in liters, after x weeks is modeled by the equation y = 100(0.78)^x.  Approximately what percent of the liquid evaporates per week?

• 22%
• 47%
• 53%
• 78%

The number of bacteria in a science experiment doubles in size every 30 minutes. At 1:30 p.m., there were 2 bacteria in the sample. How many bacteria were in the sample at 4:30 p.m.?

• 14 bacteria
• 64 bacteria
• 128 bacteria
• 256 bacteria