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学习指南 > Prealgebra

Writing Percents as Ratios

Learning Outcomes

  • Write a percent as a ratio
  • Given a ratio, write as a percent and a fraction
  How many cents are in one dollar? There are [latex]100[/latex] cents in a dollar. How many years are in a century? There are [latex]100[/latex] years in a century. Does this give you a clue about what the word "percent" means? It is really two words, "per cent," and means per one hundred. A percent is a ratio whose denominator is [latex]100[/latex]. We use the percent symbol [latex]\text{%,}[/latex] to show percent.  

Percent

A percent is a ratio whose denominator is [latex]100[/latex].
  According to data from the American Association of Community Colleges [latex]\left(2015\right)[/latex], about [latex]\text{57%}[/latex] of community college students are female. This means [latex]57[/latex] out of every [latex]100[/latex] community college students are female, as the image below shows. Out of the [latex]100[/latex] squares on the grid, [latex]57[/latex] are shaded, which we write as the ratio [latex]\frac{57}{100}[/latex]. Among every [latex]100[/latex] community college students, [latex]57[/latex] are female. The figure shows a hundred flat with 57 units shaded. Similarly, [latex]\text{25%}[/latex] means a ratio of [latex]\frac{25}{100},\text{3%}[/latex] means a ratio of [latex]\frac{3}{100}[/latex] and [latex]\text{100%}[/latex] means a ratio of [latex]\frac{100}{100}[/latex]. In words, "one hundred percent" means the total [latex]\text{100%}[/latex] is [latex]\frac{100}{100}[/latex], and since [latex]\frac{100}{100}=1[/latex], we see that [latex]\text{100%}[/latex] means [latex]1[/latex] whole.  

example

According to the Public Policy Institute of California [latex]\left(2010\right)\text{, }\text{44%}[/latex] of parents of public school children would like their youngest child to earn a graduate degree. Write this percent as a ratio. Solution
The amount we want to convert is [latex]44%[/latex]. [latex]44%[/latex]
Write the percent as a ratio. Remember that percent means per [latex]100[/latex]. [latex]\frac{44}{100}[/latex]
 

Try it

[ohm_question]146655[/ohm_question]
 

example

In [latex]2007[/latex], according to a U.S. Department of Education report, [latex]21[/latex] out of every [latex]100[/latex] first-time freshmen college students at [latex]\text{4-year}[/latex] public institutions took at least one remedial course. Write this as a ratio and then as a percent.

Answer: Solution

The amount we want to convert is [latex]21[/latex] out of [latex]100[/latex] . [latex]21[/latex] out of [latex]100[/latex]
Write as a ratio. [latex]\frac{21}{100}[/latex]
Convert the [latex]21[/latex] per [latex]100[/latex] to percent. [latex]21%[/latex]

 

try it

[ohm_question]146656[/ohm_question]
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