Intermediate Algebra
Section 9.7: Applications of Exponential and Logarithmic Functions
1.
The number of skateboarders of age
x
, in thousands, can be approximated by
x
x
N
)
9
.
0
(
1377
)
(
=
,
60
7
≤
≤
x
a.
What does
N
represent?
b.
What does
x
represent?
c.
Estimate the number of 21 year old skaters?
d.
At what age are there only about 6,300 skaters?
2.
The percentage of smokers who received telephone counseling and had successfully quit
smoking for
t
months is given by
t
t
P
)
914
.
0
(
4
.
21
)
(
=
a.
What does
P
represent?
b.
What does
t
represent?
c.
In what month will 15% of those who quit and used telephone counseling still be
smoke free?
3.
The world population,
)
(
t
P
, in billions,
t
years after 1980 can be approximated by
t
t
P
)
015
.
1
(
495
.
4
)
(
=
a.
In what year will the world population reach 7 billion?
b.
Find the doubling time.
The Exponential Growth Model:
An exponential growth model is a function of the form:
kt
e
P
t
P
0
)
(
=
,
0
k
, where
0
P
is the
population at time 0,
)
(
t
P
is the population at time
t
, and
k
is the exponential growth rate.
The
doubling time, is the amount of time needed for the population to double.
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 Spring '10
 Williamson
 Algebra, Logarithmic Functions, HalfLife, World population

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