Modeling Exponential Functions Percent Growth Decay

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=5000(0.3)^x

Which of the following functions shows an initial amount of $75 and a decrease of 12% each year?

• y = 75(12)^x

• y = 75(1 + 0.12)^x

• y = 75(0.88)^x

• y = 75(88)^x

Write an equation that models the following situation:

Samantha's hair was known to grow very rapidly. It began at a length of 6 in and grew at a rate of 14% a week.

• y=6(0.14)^x

• y=6(1+14)^x

• y=6(1+ 0.14)^x

• y=6(1 - 0.14)^x

Daniel’s Print Shop purchased a new printer for $35,000. Each year it depreciates at a rate of 5%. How much will the printer be worth in 8 years?

• $23,219.72

• $136.72

• $51,710.94

• $16,710.94

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

• y = 15(35)^x

• y = 15(1.35)^x

• y = 15(0.35)^x

• y = 35(1.15)^x

Give the rate of decay:
y = 35(0.65)^x

• 35%

• 65%

• 0.35%

• 165%

Give the rate of growth:
y = 5(1.27)^x

• 127%

• 27%

• 5

What is a, the starting term, for the function: f(x) = 800(0.85)^x?

• 800

• 0.85

• 0.15

• x

The rabbit population started at 65,000 rabbits. The population is decreasing at a rate of 1.5% each year. Write a function r(t) to represent the rabbit population after t years.

• r(t) = 65000(1 - 0.015)^t

• r(t) = 65000(1 + 0.015)^t

• r(t) = 65000(1 - 1.5)^t

• r(t) = 65000(1 + 1.5)^t

The number of mosquitoes at the beginning of the summer was 4,000. The population of mosquitoes is expected to grow at a rate of 25% a month. How long will it take the mosquito population to double?

• 3.1 months

• 1.3 months

• 6.2 months

• 7 months