Exponential Growth and Decay“Word Problem Format”Sec 10.6Sol: AII.19

Exponential Decay

tray )1( End result Start with

Rate % *change to a

decimal*

Time

A cup of coffee contains 130mg of caffeine. If coffee is eliminated from the body at a rate of 11% per hour, how long will it take for half of this caffeine to be gone from the body?

A new car costs $25,000. The value of the car decreases by 15% each year.

a) Write an exponential decay model giving the car’s value (y) in dollars after (t) years.

b) Estimate the value after 4 years.c) Estimate the time it will take for the car

to have a value of $8000.

Exponential Growth

tray )1( End result Start with

Rate % *change to a

decimal*

Time

In 1910, the population of a city was 120,000. Since then , the population has increased by exactly 1.5% per year. If the population continues to grow at this rate, what will the population be in 2010?

In 1970, the population of kern county was about 330,000. From 1970 to 200, the county’s population grew at a average annual rate of 2.4%.

a) Write the exponential growth equation.b) How many people would live in Kern

county in 1990?

A virus attacks a computer in 120 minutes. The virus grows from 40 to 326MB. Using the growth formula y = aekt, find the constant rate of the virus.

Assignments:

Classwork: WB pg 140

Homework: pg 563-564 4-12 All