# Chapter 6 test review

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```					Chapter 6 test review                              Name: ________________

1. Solving a system of two equations with two unknowns. This would be the
equation of two lines. If they were in slope intercept form, the best way to
solve for the system would be by graphing the two or by algebraic
substitution. Lets try both.
a. Graphing (by hand and by calculator)
i. Y = 3x + 5
Y = -2x + 10

b. Algebraic substitution
i. Y = -20x + 30
Y = -30x + 50

2. If a system of two equations with two unknowns is not in slope-intercept
form it may be easiest to solve the system using elimination. Here are some
examples where elimination would be the way to go.
a. 3x + 3y = 12
-3x + 6y = 15

b. 2x – 3y = 3
3x + 4y = 13
3. After we learned all the previous methods we looked at using matrices and
Guassian elimination to solve for systems of equations. Solve the following
systems using matrices. Do the first by hand and you can use your calculator
to solve the second one.
a. 3x + 4y = 23
x + 3y = 11

b. 7x + 3y = 29
3x – 2y = 19

4. We know that in the real world things get more complicated than two
equations and two unknowns, but we only go as far as three equations and
three unknowns. Use either elimination or matrices to solve for the following
system. You can use your calculator if you choose to solve the system using
matrices.
a. x + y + z = 3
x– y+z=3
2x + y + z = 4

5. Finally we looked at using matrices, not to solve systems of equations, but to
store information. When we use matrices for storing information it is
necessary that we know how to add, subtract, and multiply matrices. Use the
following matrices to perform these operations if you can. If you can’t
perform the given operation, explain why.

A=                   B=                C=                 D=

a. A + B =

b. A – B =
c. –C =

d. D * O(zero matrix) =

e. A * C =

f. C * D =

g. A * B =

6. All this knowledge is great to know, but we need to be able to apply it
somehow. Solve the following problems using the tools we learned in this
chapter.
a. The Copycat Toy Company has decided to create two new toys. One is
called the CP1 while the other is called the CP2. Each CP1 requires 15
minutes of labor while each CP2 requires 30 minutes of labor. Plastic
for each CP1 costs \$2 while plastic for each CP2 costs \$3. Yesterday
the company spent \$124 on plastic and used 18 hours of labor time in
making new figures. How many of each toy was made yesterday? (You
will need to use the fact that there are 60 minutes in an hour)
b. A steel company makes 2 types of beams. One is an I beam while the
other is a T beam. During 2002, the sales, in thousands of tons, for
each quarter (3 month period) are given in the matrix below.

During 2003, the matrix below gives the sales for each quarter.

Write a matrix representing the total sales for each quarter during
the two-year period.

c. Happy Henry’s has two local drugstores in Wisconsin. Sales at both
stores for January, February, and March in 1995 are given below for
three types of aspirins – C(children’s aspirin), R(regular aspirin), and
E(extra strength aspirin).

Because of a cold winter in 1996, sales doubled at store A and tripled
at store B. Write a matrix for total sales in 1996 for the three
months.

What matrix operations did you perform to answer this question?

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