Percent Growth or Decay

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

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

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

A bird species is decreasing at a rate of 2% each year. If there are currently 150,000 of these birds, which function would determine the number of birds B, after n years?

• B = 15000(0.02)ⁿ

• B = 15000(1.02)ⁿ

• B = 15000(0.98)ⁿ

• B = 15000(0.80)ⁿ

There were 417 cell phones sold at an electronics store in January. Since then, cell phone sales at this store have increased at a rate of 3.75% per month. At this rate of growth, which function can be used to determine the monthly cell phone sales x months after January?

• f(x) = 417(3.75)^x

• f(x) = 417(0.0375)^x

• f(x) = 417(1.0375)^x

• f(x) = 417(1.375)^x

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

• A

• B

• C

• D

Look at the following exponential equation and tell the percent of Growth or Decay;

y = 1.5(.89)^x

• 1.5% Growth

• 11% Decay

• 89% Decay

• 89% Growth

Look at the following exponential equation and tell the percent of Growth or Decay;

y = 80(1.15)^x

• 15% Decay

• 80% Growth

• 115% Growth

• 15% Growth

• A

• B

• C

• D