1. 8-8 Exponential Growth and Decay

2. RULE-Exponential Growth

3. Modeling Exponential Growth
In 1998, a certain town had a population of about 13,000 people. Since 1998, the population has increased about 1.4% a year.
Write an equation to model the population increase.
Use your equation to approximate the population in 2006.

4. Compound Interest Interest Period
When a bank pays interest on both the and an account has already earned.
Interest Period
The length of time over which interest is calculated

5. Compound interest formula

6. Compound interest
Suppose your parents deposited $1500 in an account paying 3.5% interest compounded annually (once a year) when you were born. Find the account balance after 18 years.

7. You try:
Suppose you deposit $1000 in a college fund that pays 7.2% interest compounded annually. Find the account balance after 5 years.

8. When it’s not annually…

9. More compound interest
Suppose you deposit $1000 in a college fund that pays 7.2% interest compounded quarterly. Find the account balance after 5 years.

10. Rule-Exponential Decay

11. Modeling Exponential Decay
Since 1980, the number of gallons of whole milk each person in the U.S. drinks each year has decreased by 4.1% each year. Un 1980, each person drank an average of 16.5 gallons of whole milk a year.
Write an equation to model the gallons of whole milk drunk per person.
Use your equation to find the approximate consumption per person of whole milk in 2016.

12. You try.
Suppose the population of a certain endangered species has decreased 2.4% each year. Suppose there were 60 of these animals in a given area in 1999
Write an equation to model the number of animals in this species that remain alive in that area
Find the approximate number of animals remaining in 2016.

13. Real World Problem Solving
The half life of radioactive substances is the length of time it takes for one half of the substance to decay into another substance.
Technetium-99 has a half life of 6 hours. Suppose a lab has 80mg of technetium-99. How much technetium-99 is left after 24 hours?