solving percent problems with proportions section 7.3
DESCRIPTION
Since the ratio is equal to the ratio, we have the proportion ratio, we have the proportion called the percent proportion. Writing Percent Problems as Proportions..., 3 Martin-Gay, Prealgebra, 5edTRANSCRIPT
Solving Percent Problems Solving Percent Problems with Proportionswith Proportions
Section 7.3
To understand the proportion To understand the proportion method, recall that 30% means themethod, recall that 30% means the
ratio of 30 to 100, or .ratio of 30 to 100, or .
30%
Writing Percent Problems as Writing Percent Problems as ProportionsProportions
30100
30100
310
2Martin-Gay, Prealgebra, 5ed
Since the ratio is equal to theSince the ratio is equal to the
ratio , we have the proportionratio , we have the proportion
called the called the percent proportionpercent proportion..
Writing Percent Problems as Writing Percent Problems as Proportions . . .Proportions . . .
,,
301003
1030 3
100 10
3Martin-Gay, Prealgebra, 5ed
always 100
or
percentbase
amount
Percent ProportionPercent Proportion
amount percentbase 100
100a pb
4Martin-Gay, Prealgebra, 5ed
When we translate percent problems to When we translate percent problems to proportions, the proportions, the percentpercent can be can be identified by looking for the symbol % identified by looking for the symbol % or the word or the word percentpercent. The . The basebase usually usually follows the word follows the word ofof. The . The amountamount is the is the part compared to the whole.part compared to the whole.
5Martin-Gay, Prealgebra, 5ed
Helpful HintHelpful Hint
Part of Part of ProportionProportion
How It’s How It’s IdentifiedIdentified
Percent Percent % or percent% or percentBase Base Amount Amount
Appears after Appears after of of
Part compared to Part compared to whole whole
6Martin-Gay, Prealgebra, 5ed
What number is 20% of 8?
amount percent base
amountbase
percent
Solving Percent Proportions for Solving Percent Proportions for the Amountthe Amount
208 100a
7Martin-Gay, Prealgebra, 5ed
20 is 40% of what number?
amount percent base
amountbase
percent
Solving Percent Proportions for Solving Percent Proportions for the Basethe Base
20 40100b
8Martin-Gay, Prealgebra, 5ed
What percent of 40 is 8?
amountpercent base
amountbase
percent
Solving Percent Proportions for Solving Percent Proportions for the Percentthe Percent
840 100
p
Helpful HintHelpful HintRecall from our percent proportion that this number, p already is a percent. Just keep the number the same and attach a % symbol. 9
Helpful HintHelpful Hint
A ratio in a proportion may be simplified A ratio in a proportion may be simplified before solving the proportion. The before solving the proportion. The unknown number in bothunknown number in both
andand
is 20.
6 304 b
3 302 b
10Martin-Gay, Prealgebra, 5ed