Pre-Algebra
Glencoe 9.1
A ratio is a comparison
of two numbers or
measures using division.
A ratio can be written three
ways:
3:5
3/5
3 to 5
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Ratios are often
expressed as fractions in
simplest or as a decimal.
5
1
 or .25
20 4
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A ratio is the comparison of two numbers with the same
units by division. A ratio may be written in three ways.
2 to 3
2:3
2
3
What ratios can we form from the tiles
above?
part  12 to 8
part 
part 
whole 
12
20
whole 
part 
20
12
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Create as many ratios as possible.
Write each ratio three different
ways.
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Simplest Form
• Write the ratio 50 to 300
in simplest form.
1
50

300 6
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Simplest Form
• Write the ratio 60¢ per dozen
in simplest form.
5
60

1
12
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Look over the ratios you have written. Is
there another way that you can write those
ratios?
The ratio illustrated here is
four filled cells to ten total
cells.
The ratio shown here is
two filled cells to five
total cells.
What do you know about these two ratios?
How can you prove your answer?
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Unit Rate
To find the Unit Rate, you
would find the cost or
amount for 1. Or the rate
when the denominator is 1.
“How much for just 1?”
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Unit Rate
If it costs $78 for 13
sandwiches, What is the unit
rate?
$78 13  $6 each
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The cost of a 12-ounce box
of Cheerios is $3.29. Publix
brand Cheerios cost $4.89
for an 18-ounce box. Find
the unit rate to find the
better buy.
3.29
4.89
 .274
 .271
12
18
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Mile per Gallon
• M.P.G. stands
for miles per
gallon and is
usually used for
gas mileage in
cars.
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Unit Rate
• If it takes 11 gallons
to drive 250 miles,
What is the unit rate
or m.p.g.?
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Solving Word Problems
250
x
•Write problem as proportions:

11
1
•Solve using cross multiplication.
250(1)  11X
250 11X

11
11
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Now you try it!
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