| Algebra 1 Notes
Chapter Eight
Section 8.1
Section 8.2
Section 8.3
Section 8.4
Section 8.5
Section 8.6
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Section 8.4 Using
Systems of Equations
(Examples provided by Prentice
Hall)
Part I: Problem Solving: Using Systems of Equations
Translate into a system and solve.
| Example
1 |
|
The
Acme Transportation company owns three times as many mini-buses
as regular buses. There are 60 more mini-buses than regular
buses. How many of each does Acme own?
Let m be the number of mini-buses. Let r be the
number of regular buses.
m = 3r
m = r + 60
Substitute 3r for m in the second equation.
3r = r + 60
2r = 60
r = 30
m = 3r
m = 90
Acme owns 90 mini-buses and 30 regular buses. |
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| Example
2 |
Bob
is 6 years older than Fred. Fred is half as old as Bob. How old
are they?
Let b be the age of Bob. Let f be the age of Fred.
| b
= f + 6 |
|
(1) |
| f
=(1/2)b |
(2) |
Substitute for f in (1).
b = (1/2)b + 6
(1/2)b = 6
b = 12
Substitute in (2).
f = (1/2) (12)
f = 6
Bob is 12 and Fred is 6. |
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| Example
3 |
Computer
Information Inc. charges $10 per month plus $7 per minute for
computer access to its information. Data Access Corporation
charges $20 per month plus $5 per minute. For what number of
minutes are the charges the same?
Let c be the cost in dollars. Let t be the time
used, in minutes. For Computer Information Inc. the cost is c
= 10 + 7t. For Data Access Corp. the cost is c =
20 + 5t.
Substituting 10 + 7t for c, 10 + 7t = 20 +
5t. Solve for t.
2t = 10
t = 5
The companies charge the same amount for 5 minutes. |
Take class notes.
Before starting your homework, rework the
examples that are illustrated in this section of your textbook and the
examples that I demonstrated in class.
Then do your homework.
Write down questions (examples or concept
that you do not understand).......then.............. Ask these questions
in class.
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