6.9小数表示百分比

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  小数表示百分比

  

  [Figure 1]

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  Jessica’s New Year’s resolution is to run one mile on her treadmill every day. On a random day in January, her treadmill readout shows that she ran 2.9 miles. What percent of her running goal did she achieve that day?
  ::杰西卡的新年决心是每天在跑步机上跑一英里。 在1月的一天中,她的跑步机读数显示她跑了2.9英里。 她的跑步机目标中有多大比例实现了这一天?

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  In this concept, you will learn how to write decimals as percents.
  ::在这个概念中,你会学习如何以百分比来写小数。

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  Writing Decimals as Percents
  ::将十进制数写入百分比

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  You can write  , and you can also write decimals as percents.
  ::您可以写,您也可以以百分数来写小数。

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  First, move the  decimal point  two places to the right. Add zeros to the right of the decimal point as placeholders, if necessary.
  ::首先,将小数点 2 移到右边。必要时,在小数点右侧作为占位符增加零。

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  Then, write a % symbol after the resulting number.
  ::然后,在生成数字之后写一个%的符号。

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  Let’s apply these steps to an example.
  ::让我们把这些步骤应用到一个例子上。

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  Write 0.78 as a percent.
  ::将0.78的百分率写成0.78。

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  This decimal is already written in hundredths because there are two digits after the decimal point. All you have to do is move the decimal two places to the right and add a percent sign.
  ::此小数点已经以百分百表示, 因为小数点后有两个位数。 您只需要将小数点后的两个位数移到右边, 并添加一个百分比符号 。

  $$\begin{array}{r}0.78=78\mathrm{\%}\end{array}$$

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  The answer is 0.78 written as a percent is 78%.
  ::答案是0.78 写成百分比为78%。

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  Let’s try another example.
  ::让我们再试一个例子。

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  Write 0.345 as a percent.
  ::0.345 写成百分比为0.345。

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  This decimal is written in thousandths because there are three digits after the decimal point. You only need to move the decimal point two places to the right to make it a percent, so you will have a digit left over that remains after the decimal point.
  ::此小数数以千分之一写, 因为小数点之后有三个位数。 您只需将小数点 2 位移到右侧, 才能将其设定为%, 这样您就会剩下一个位数, 留到小数点之后 。

  $$\begin{array}{r}0.345=34.5\mathrm{\%}\end{array}$$

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  The answer is 0.345 written as a percent is 34.5%.
  ::答案是0.345 写成百分比为34.5%。

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  Notice that sometimes you can have a decimal in a percent. In this case, it means that you have 34 and one-half percent. Not all percents are whole percents.
  ::注意有时您可以用小数点以百分之一表示小数点。 在这种情况下,这意味着您有34.5 %。并非所有的百分率都是完整的。

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  Let’s try one more example.
  ::让我们再举一个例子。

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  Write 3.5 as a percent.
  ::3.5 以百分比表示。

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  This decimal is written with a whole number and five tenths. You still move the decimal point to the right two places, adding a  zero  as a placeholder. Notice that because you have a whole number in front of the decimal point that the percent will be greater than 100.
  ::此小数点以整数和十进制写成。 您仍然将小数点移到正确的两个位子, 作为占位符添加 0 。 请注意, 因为小数点前面有一个整数, 百分数将大于 100 。

  $$\begin{array}{r}3.5=350\mathrm{\%}\end{array}$$

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  The answer is 3.5 written as a percent is 350%.
  ::答案是3.5, 写成百分比是350%。

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  Examples
  ::实例

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  Example 1
  ::例1

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  Earlier, you were given a problem about Jessica and her New Year’s resolution.
  ::更早之前,你曾遇到Jessica和她的新年决议的问题。

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  One day in January her treadmill readout recorded that she ran 2.9 miles. What percent of her 1-mile running goal did she achieve that day?
  ::1月的一天,她的跑步机读数记录了她跑2.9英里。 她的1英里跑程目标中,有百分之几达到这一天?

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  This decimal is written with a whole number and nine tenths.
  ::此小数点为整数和十分之九。

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  First, move the decimal point to the right two places.
  ::首先,将小数点移到正确的两个位置。

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  Then, notice that because you have a whole number in front of the decimal point that the percent will be greater than 100.
  ::然后,注意,因为您在小数点前有一个完整的数字, 百分数将大于100。

  $$\begin{array}{r}2.9=290\mathrm{\%}\end{array}$$

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  The answer is Jessica ran 290% of her 1-mile goal that day.
  ::答案是杰西卡在那天的一英里目标中 跑了290%

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  Example 2
  ::例2

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  Write 0.6 as a percent.
  ::0.6%写成百分之0.6

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  This decimal is written in tenths because there is only one digit after the decimal point. When you move the decimal two places to the right, you will therefore need to add a zero placeholder.
  ::此小数点以十进制写入, 因为小数点之后只有一位数。 当将小数点后的两个位移到右边时, 您需要添加一个零占位符 。

  $$\begin{array}{r}0.6=60\mathrm{\%}\end{array}$$

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  The answer is 0.6 written as a percent is 60%.
  ::答案是0.6 写成百分比为60%。

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  Example 3
  ::例3

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  Write 0.45 as a percent.
  ::写0.45 百分比。

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  This decimal is already written in hundredths because there are two digits after the decimal point. Therefore, all you have to do is move the decimal two places to the right and add a percent sign.
  ::此小数点已经以百分百计, 因为小数点后有两个位数。 因此, 您只需要将小数点后的两个位数移到右边, 并添加一个百分比符号 。

  $$\begin{array}{r}0.45=45\mathrm{\%}\end{array}$$

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  The answer is 0.45 written as a percent is 45%.
  ::答案是0.45, 写成百分比为45%。

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  Example 4
  ::例4

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  Write 2.5 as a percent.
  ::2.5 以百分比写。

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  This decimal is written with a whole number and five tenths. You still move the decimal point to the right two places, adding a zero as a placeholder. Notice that because you have a whole number in front of the decimal point that the percent will be greater than 100.
  ::此小数点以整数和十进制写成。 您仍然将小数点移到正确的两个位子, 作为占位符添加 0 。 请注意, 因为小数点前面有一个整数, 百分数将大于 100 。

  $$\begin{array}{r}2.5=250\mathrm{\%}\end{array}$$

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  The answer is 2.5 written as a percent is 250%.
  ::答案是2.5, 写成百分比是250%。

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  Example 5
  ::例5

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  Write 0.875 as a percent.
  ::将0.875写为百分比。

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  This decimal is written in thousandths because there are three digits after the decimal point. You only need to move the decimal point two places to the right to make it a percent, so you will have a digit left over that remains after the decimal point.
  ::此小数数以千分之一写, 因为小数点之后有三个位数。 您只需将小数点 2 位移到右侧, 才能将其设定为%, 这样您就会剩下一个位数, 留到小数点之后 。

  $$\begin{array}{r}0.875=87.5\mathrm{\%}\end{array}$$

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  The answer is 0.875 written as a percent is 87.5%.
  ::答案是0.875, 写成百分比为87.5%。

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  Review
  ::回顾

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  Write the following decimals as percents.
  ::以下小数位数以百分比表示。

  1. 0.45
  2. 0.3
  3. 0.675
  4. 0.9
  5. 0.08
  6. 0.785
  7. 0.22
  8. 0.095
  9. 0.54
  10. 0.275
  11. 0.04
  12. 0.045
  13. 0.112
  14. 4.6
  15. 0.672

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  Review (Answers)
  ::回顾(答复)

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  Click   to see the answer key or go to the Table of Contents and click on the Answer Key under the 'Other Versions' option.
  ::单击可查看答题键, 或转到目录中, 单击“ 其他版本” 选项下的答题键 。

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  Resources
  ::资源