Exponential Growth and Decay Formula

Identify whether the function is exponential GROWTH or DECAY.

y = 1200(1/9)^x

• Growth

• Decay

A population of 1500 deer decreases by 1.5% per year. At the end of 10 years, there will be approximately 1290 deer in the population.

Which function can be used to determine the number of deer, y, in this population at the end of t years?

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?

An antibiotic is introduced into a colony of 12,000 bacteria during a laboratory experiment. The colony is decreasing by 14.9% per minute.

Which function can be used to model the number of bacteria in the colony after x minutes?

A population of fish starts at 8,000 and increases by 6% per year.

What is the fish population in 10 years?

If the rate of increase is 5%, what do you plug in for r in the exponential growth?

• 5

• 0.5

• 0.05

• 0.005

Before plugging in the rate (r) into the exponential equation, you should ________.

• divide the % by 100

• multiply the % by 100

• divide the % by 10

• multiply the % by 10

Daniel’s Print Shop purchased a new printer for $35,000. Each year it depreciates at a rate of 5%.

Which formula can be used to find out how much the printer will be worth in 8 years?

A population of fish starts at 8,000 and increases by 6% per year.

Which exponential function can be used to find the fish population in 10 years?