Chapter 8 Ratio, Proportion, and Percent

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Chapter 8Ratio, Proportion, and Percent
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Ratios
In the Real World School Orchestras In some
school orchestras, all of the instruments are
stringed violins, violas, cellos, and double
basses. How can you compare the numbers of
instruments in the orchestras?
One way to compare the numbers of instruments is
to use a ratio.
There are 3 ways to write a ratio
a b
a to b
a b
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Writing a Ratio in Different Ways
In the example on the last slide, if there are 18
violins, 8 violas, 6 cellos, and 3 double basses,
you can write a ratio to tell how many violas
there are to the total number of instruments.
To do that, you simply place how many violas, 8,
over how many total instruments, 35.
8 35
835
8 to 35
Note Just as a fraction, you need to reduce if
necessary.
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Writing Ratios in Simplest Form
Using the same information of instruments 18
violins, 8 violas, 6 cellos, and 3 double basses,
write the ratio of the number of double basses to
the number of cellos in simplest form.
1 2
3 double basses 6 cellos
Reduced gives me
So, I can write my answer as the fraction form
above or also as 1 2 or 1 to 2.
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Writing Ratios in Simplest Form Continued
Using the same information of instruments 18
violins, 8 violas, 6 cellos, and 3 double basses,
write the ratios in 3 ways for the following
18 35
Violins to total instruments
18 to 35
18 35
8 3
8 to 3
8 3
Violas to double basses
6 18
1 3

Number of cellos to the number of violins
1 to 3
1 3
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Writing Equivalent Ratios
To get an equivalent ratio, you can simply
multiply or divide the numerator and denominator
by the same number.
So, multiply the top by 4, too.
20
X 4
5 15
? 60
Complete the statement to write
equivalent ratios.
X 4
Ask yourselfHow did I get from 15 to 60?
5 15
20 60
So,

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Comparing Ratios Using Decimals
3 4
Football Allen completes of his pass
attempts. Mike completes 7 out of every 10 pass
attempts. Who has a better record?
You can compare the 2 scores by comparing the
fractions, but also by writing the ratio as a
decimal.
3 4
7 10
Allen
0.75
Mike
0.70
Because 0.75 is greater than 0.70, Allen has a
better record.
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Now You Try!
Copy and complete the statement.
4
X 5
5
10
2 3
? 15
7 ?
35 50
20 32
5 ?



5
4
10
X 5
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Copy and complete the statement using lt, gt, or .
5 20
4 10
3 5
?
?
?
18 out of 30
24 ___ 735
0.25
lt
0.40
0.60

0.60
0.5
0.2
gt
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Now You Try Continued
5 12
Write the ratio in 2 other ways.
5 to 12
5 12
Write the ratio in simplest terms.
6 15
8 20
12 3
2 5
2 5
4 1



Divide both by 3
Divide both by 4
Divide both by 3