Download Growth VS Decay and Percent Growth and Decay

Warm Up
1) Change from percent to decimal 56%
2) Tom had four flowers patch. The flowers grew
exponentially, doubling every 8 hours.
1)
Write the equation to model this situation.
2)
How many flowers would Tom have after 2 days?
Exponential Functions Remember!
An exponential function is a function with
the general form
y=
x
ab
a ≠ 0 and b > 0, and b ≠ 1
A and B
A Starting Value
B is direction
Growth
b>1
Decay
0<b<1
Y-intercept and Growth vs. Decay
Identify each y-intercept and whether it is a growth or decay
1. Y= 3(1/4)x
5. Y = 4500(.4)x
2. Y= .5(3)x
6. Y = 76(3/4)x
3. Y = (.85)x
4. Y = 300(1.3)x
Increase and Decrease by percent
 Exponential Models can also be used to
show an increase or decrease by a
percentage.
Increase and Decrease by percent
The rate of increase or decrease is a percent,
we use a change factor/base
of 1 + r or 1 – r.
Growth
b>1
Change factor
(1 + r)
Decay
.
0<b<1
Change Factor
(1 - r)
Percent to Change Factor
When something grows or decays by a
percent, we have to add or subtract it from
one to find b.
1. Increase of 25% 2. increase of 130%
2. Decrease of 30% 4. Decrease of 80%
Growth Factor to Percent
Find the percent increase or decease from the
following exponential equations.
1. Y = 3(.5)x
2. Y = 2(2.3)x
3. Y = 0.5(1.25)x
Percent Increase and Decrease
A dish has 212 bacteria in it. The population of
bacteria will grow by 80% every day.
How many bacteria will be present in 4 days?
Percent Increase and Decrease
 The house down the street has termites in the
porch. The exterminator estimated that there are
about 800,000 termites eating at the porch. He
said that the treatment he put on the wood would
kill 40% of the termites every day.
 How many termites will be eating at the porch in 3
days?