Exponential Growth

1
Exponential Growth Decay

• Lesson 8.7

2
Growth goes up in value, use this formula!
y c(1r)t 1rgt1 Decay goes down in
value, use this formula! y c(1-
r)t 1- r lt1
3
Example You buy a new 10 speed bike for 150.
It loses value at a rate of 15 per year. What
is its worth in 3 years?
Worth cost(rate)years w c(1-0.15)3
(a loss means 15) w 150(.85)3 w
92.12 The bike was only worth 92.12 in 3 years.
4
Identify the following as growth or decay

• y 500(1.20)5
• y 375(.078)t
• y 5(1.078)6
• y 30(.99)4

5
Write a general equation for the following

• You purchased a car for 35,000. The minute you
  drove it off the lot it started going down in
  value by 1.3. Write an equation for its value
  in the future.
• You just purchased a painting as an investment
  and it is suppose to appreciate it value at a
  rate of 3.65 each year. Write an equation for
  its value in the future.

V 35,000(0.987)t
V P(1.0365)t