Name__________________________________________Block_____ Exponential Growth and Decay Solve each growth and decay problem. 1) E.coli bacteria double in population every thirty minutes. If the initial population is 85, what is the population of bacteria after three hours? After one day?

2) You decide to borrow money at 22% interest per year, how much will you owe on a loan of $5,000 after one year? What about after three years?

3) The population of Bloom Falls, Mass. (population 937) is slowly moving to a bigger city. Every year the population drops by 4.5%. What is the population after 3 years?

4) You bought a Boston Whaler in 2004 for $12,500. The boat's value depreciates by 7% a year. How much is the boat worth in 2012? What will it be worth in 2020?

5) The original value of a painting is $1400, and the value increases by 9% each year. Write an exponential growth function to model this situation. Then find the value of the painting in 25 years.

6) The population of a town is decreasing at a rate of 1% per year. In 2000 there were 1300 people. Write an exponential decay function to model this situation. Then find the population in 2008.

7) Evaluate the expression for (a) x   2 and (b) x  3. a)

3x

b)

5  2x

c)

3  2x

7) Tell whether the function represents exponential growth or exponential decay. Then use a sticky graph to graph the function. a)

y  5x

d)

y  3

 2

b)

x

e)

y  3x

y  1.6

c)

x

5

y  1

f) y  0.5

x

x