Ratios

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Ratios Unit Rates

• 6-1

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VOCABULARY

• Ratio a comparison of two quantities by
  division
• Rate ratio that compares quantities in
  different units
• Unit Rate a rate that has a denominator of 1

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WRITING RATIOS
Key Concepts A ratio compares two quantities
through division. You can write a ratio in many
different ways.
Statistics In the United States, about 10 out
of every 15 people eligible to vote are
registered to vote. The numbers 10 and 15 form
a ratio.
10 to 15 1015 10/15
10 or 2
15 3
Note When writing in fraction form, always
simplify!
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Examples

• 1. 5 inches of snow in 10 hours
• Ratio _____ Rate _____ inches per hour
• 2. 95 copies in 5 minutes
• Ratio _____ Rate _____ copies per min
• 3. 5 lawns mowed for 125 dollars
• Ratio _____ Rate _____ dollars per lawn
• 4. 4 bags with 360 cans
• Ratio _____ Rate _____ cans per bag

0.5
5/10
95/5
19
25
125/5
360/4
90
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Example

• A survey asked students whether they had
  after-school jobs. Write each ratio as a
  fraction in simplest form.

Response Number
Have a job 40
Dont have a job 60
TOTAL 100
a. Students with jobs to students without jobs
Students with jobs 40 2 Students w/o jobs
60 3
b. Students without jobs to all students surveyed
Students w/o jobs 60 3 Students surveyed
100 5
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FINDING RATES AND UNIT RATES

• We know that a ratio that compares quantities
  with different units of measurement is called a
  rate.
• A unit rate is a rate that has a denominator of
  1. We will use unit rates when comparing prices,
  gas mileage, speed, etc.

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Example 2

• Unit Prices The table shows prices for
  different sizes of the same dish detergent.
  Which size has the lowest unit price?

Regular price 1.20 volume
12 fl. oz
Size Volume (fl. oz.) Price
Regular 12 1.20
Family 28 2.24
Economy 40 3.60
.10/fl. oz.
Family price 2.24 volume
28 fl. oz
.08/fl. oz.
Economy price 3.60 volume
40 fl. oz
Therefore, the family size has the lowest unit
price.
.09/fl. oz.