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Proportions, ratios, and rates are similar to equivalent fractions.
When setting up these types of problems be sure to keep
the units in the same place in each fraction
(numerator/denominator).
Use the samples below
as a guide to help you in solving problems with proportions,
ratios, and rates. .
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Example
one: Using Proportions
Lisa paid $3 for six
donuts. How much would
she pay for three dozen donuts?
Set up the proportion as
Use x for the unknown dollar amount.
36 is used since three dozen = 36.
To
solve, cross multiply…
6x =
3(36)
6x =
108
X =
$18
Lisa would pay
$18 for three dozen donuts.
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Example
two:
Using Ratios
Problem:
The ratio of dogs
to cats in the animal shelter is 2:5.
If there are 91 dogs and cats how many cats are there in
the shelter?
Solution:
Since
the ratio tells us there are 5 cats out of 7 total (2+5=7)
then:
To
solve, cross multiply…
7x =
5(91)
7x =
455
X = 65
There are 65
cats in the animal shelter.
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Example
three: Using Rates
Problem:
Mrs. Adams
can tie 25 bows in 3 minutes.
How many bows can she tie in one hour at that rate?
Solution:
Set up the rate
as
Since there are 60 minutes in one hour…
To
solve, cross multiply…
3x
= 60(25)
3x
= 1500
X
= 500
Mrs. Adams
can tie 500 bows in one hour.
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 Remember:
Remember that proportions, ratios, and rates are similar to equivalent fractions.
When setting up these types of problems be sure to keep
the units in the same place in each fraction
(numerator/denominator).
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