Exponential growth/decay and Compounding Interest

The population of a school is 800 students and is increasing at a rate of 2% per year. Use an exponential function to find the population of the school after 9 years.

Round to the nearest whole number.

A pot of soup, currently 62°C above room temperature, is left out to cool. If that temperature difference decreases by 6% per minute, then what will the difference be in 4 minutes?

If necessary, round your answer to the nearest tenth.

During a certain period of time, about 70 northern sea otters had an annual growth of 18%. Use an exponential function to find the number of sea otters after 4 years.

Round to the nearest whole number.

It is estimated that the population of the world is increasing at an average annual rate of 1.3%. If the 2008 population was about 6,641,000,000 predict the 2020 population.

• 7,453,435,556 people

• 6,745,343,556 people

• 7,754,375,446 people

• 2,878,556,791 people

Exponential growth is  $y=a\left(1+r\right)^x$  , and exponential decay is  $y=a\left(1-r\right)^x$  .

What does "a" represent?

• Initial amount

• Rate of growth or decay

• Time

• End amount

What is the formula for exponential growth?

• $f\left(x\right)=a\left(1-r\right)^x$

• $f\left(x\right)=a\left(1+r\right)^x$

Exponential growth is  $y=a\left(1+r\right)^x$  , and exponential decay is  $y=a\left(1-r\right)^x$  .

What does "x" represent?

• Initial amount

• Rate of growth or decay

• Time

• End amount

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

What is the formula for exponential decay?

• $f\left(x\right)=a\left(1-r\right)^x$

• $f\left(x\right)=a\left(1+r\right)^x$

Nathan bought a VERY fancy boat for about $125,000. If the boat's value depreciates at the rate of 15% per year, what is the value of the boat at the end of 10 years?

• $12,512.50

• $18,750

• $24,609.30

• $505,694.72