8.17%的数字

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  %的数字

  

  [Figure 1]

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  Lee loves basketball. He hopes to be just as good as his favorite player, Kobe Bryant. On average, Kobe makes 83% of all his free throws. Lee practices shooting 50 free throws every day. If Lee wants to shoot free throws as well as Kobe, how many does he need to make?
  ::李热爱篮球。他希望和他最喜欢的球员神户·布赖恩特一样好。平均而言,神户占他所有免费投球的83%。李家每天射击50次。如果李家和神户一样想投免费投球,他需要投多少?

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  In this concept, you will learn how to find the percent of a number.
  ::在这个概念中,你会学会如何找到一个数字的百分率。

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  Finding the Percent of a Number
  ::查找数字的百分率

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  A  percent  is a ratio that describes a quantity out of 100. A percent is also a part of a whole. Finding the percent of a number is the part of a number that is equivalent to the percent. You can find the percent of a number two ways. One method is to use a  proportion , an equation that shows  .
  ::A% 是一个比例表示在100中的数量的比例, A%也是整体的一部分。 发现一个数字的%是数字的一部分, 相当于%。 您可以找到数字的%, 一种方法是使用比例, 一种表示比例的方程式 。

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  Let’s, find 10% of 25 using a proportion.
  ::让我们在25人中有10%使用比例。

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  First, write the percent as a fraction. 10% is also 10 out of 100.
  ::首先,将百分比作为一个分数来写。 10%也是100分中的10分之一。

  $$\begin{array}{r}10\mathrm{\%}=\frac{10}{100}\end{array}$$

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  Next, write a proportion to find the equivalent fraction of 10% of 25. The second fraction is the unknown quantity, represented by  $\begin{array}{r}x\end{array}$ , over the whole, 25.
  ::接下来,写出一个比例,以找到25分之10%的相等分数。 第二个分数是未知数量,以x表示,整个25分数。

  $$\begin{array}{r}\frac{10}{100}=\frac{x}{25}\end{array}$$

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  Then, cross multiply to find the cross products. To cross multiply, multiply the  numerator  of one fraction with the  denominator  of the other fraction. The products should be equal.
  ::然后,交叉乘以找到交叉产品。要交叉乘以,将一个分数的分子数与另一个分数的分母数乘以一个分数。产品应该是相等的。

  $$\begin{array}{r}10(25)=100x\end{array}$$

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  Finally,  simplify  the equation to solve for  $\begin{array}{r}x\end{array}$ . Multiply 10 by 25 and  divide  both sides by 100.
  ::最后,简化方程以解答 x. 。乘以 10 乘以 25, 双方平分100。

  $$\begin{array}{r}\begin{array}{rcl}10(25)& =& 100x\\ \frac{250}{100}& =& \frac{100x}{100}\\ 2.5& =& x\end{array}\end{array}$$

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  10% of 25 is 2.5.
  ::25人中10%为2.5人。

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  Let’s review the steps of using a proportion.
  ::让我们审查使用比例的步骤。

  

  [Figure 2]

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  Another method is to use key words and multiplication. Let’s look again at the problem.
  ::另一种方法是使用关键词和乘法。 让我们再看看这个问题。

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  What 10% of 25?
  ::25分的10%是多少?

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  First, look for key words that suggest an operation. The word “of” tells you to multiply 25 by 10%.
  ::首先,寻找显示操作的关键字。 “ of” 字会告诉你乘以 25 乘以 10% 。

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  Next, convert 10% to a decimal.
  ::下一步,将10%转换为小数点。

  $$\begin{array}{r}10\mathrm{\%}=0.1\end{array}$$

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  Then, write an equation to find the unknown number,  $\begin{array}{r}x\end{array}$ .
  ::然后写一个方程式 找到未知的数字 x

  $$\begin{array}{r}x=25\times 0.1\end{array}$$

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  Finally, solve for  $\begin{array}{r}x\end{array}$  by multiplying 25 by 0.1.
  ::最后, X 以25乘以 0.1 来解析 。

  $$\begin{array}{r}25\times 0.1=2.5\end{array}$$

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  The answer is the same. 10% of 25 is 2.5.
  ::答案是一样的 25人中10%是2.5

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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 Lee practicing his free throw.
  ::之前,你遇到一个问题 李练习他的自由投球。

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  Lee wants to make just as many free throws as Kobe. To find out how many he needs to make, Lee must multiply 50 by 83%.
  ::Lee想做和神户一样的免费投球。为了弄清楚他需要做多少,Lee必须乘以50乘以83%。

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  First, convert 83% to a decimal.
  ::首先,将83%转换为小数点。

  $$\begin{array}{r}83\mathrm{\%}=0.83\end{array}$$

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  Next, write an equation to find the unknown number,  $\begin{array}{r}x\end{array}$ .
  ::下一步,写一个方程式以找到未知数字 x。

  $$\begin{array}{r}x=50\times 0.83\end{array}$$

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  Then, solve for  $\begin{array}{r}x\end{array}$  by multiplying 50 by 0.83.
  ::然后,用乘50乘0.83来解答 x。

  $$\begin{array}{r}\begin{array}{rcl}50\times 0.83& =& 41.50\\ x& =& 41.5\end{array}\end{array}$$

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  83% of 50 is 41.5. Lee needs to make at least 41 out of 50 free throws to be just as good as Kobe.
  ::百分之八十三是百分之八十三是百分之四十一。 李必得在五十次免费投球中至少做41次 才能和神户一样好。

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  Example 2
  ::例2

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  What is 15% of 200?
  ::200的15%是多少?

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  The keyword “of” tells you to multiply 200 by 15%. First, convert 15% to a decimal.
  ::关键字“of”指示您将200乘以15%。首先,将15%转换为小数。

  $$\begin{array}{r}15\mathrm{\%}=0.15\end{array}$$

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  Next, write an equation to find the unknown number,  $\begin{array}{r}x\end{array}$ .
  ::下一步,写一个方程式以找到未知数字 x。

  $$\begin{array}{r}x=200\times 0.15\end{array}$$

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  Finally, solve for  $\begin{array}{r}x\end{array}$  by multiplying 200 by 0.15.
  ::最后,通过乘以200乘以0.15来解答 x。

  $$\begin{array}{r}\begin{array}{rcl}200\times 0.15& =& 30.00\\ x& =& 30\end{array}\end{array}$$

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  15% of 200 is 30.
  ::200的15%是30

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  Example 3
  ::例3

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  What is 10% of 54?
  ::54分的10%是多少?

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  First, convert 10% to a decimal.
  ::首先,将10%转换为十进制。

  $$\begin{array}{r}10\mathrm{\%}=0.1\end{array}$$

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  Next, write an equation to find the unknown number,  $\begin{array}{r}x\end{array}$ .
  ::下一步,写一个方程式以找到未知数字 x。

  $$\begin{array}{r}x=54\times 0.1\end{array}$$

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  Then, solve for  $\begin{array}{r}x\end{array}$  by multiplying 54 by 0.1
  ::然后,将54乘以 0.1 来解析 x 的答案

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  10% of 54 is 5.4.
  ::54人中有10%是5.4人。

  $$\begin{array}{r}\begin{array}{rcl}54\times 0.1& =& 5.4\\ x& =& 5.4\end{array}\end{array}$$

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  Example 4
  ::例4

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  What is 25% of 80?
  ::80的25%是多少?

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  First, convert 25% to a decimal.
  ::首先,将25%转换为小数点。

  $$\begin{array}{r}25\mathrm{\%}=0.25\end{array}$$

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  Next, write an equation to find the unknown number,  $\begin{array}{r}x\end{array}$ .
  ::下一步,写一个方程式以找到未知数字 x。

  $$\begin{array}{r}x=80\times 0.25\end{array}$$

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  Then, solve for  $\begin{array}{r}x\end{array}$  by multiplying 80 by 0.25.
  ::然后,通过乘以80乘以0.25来解析 x。

  $$\begin{array}{r}\begin{array}{rcl}80\times 0.25& =& 20.00\\ x& =& 20\end{array}\end{array}$$

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  25% of 80 is 20.
  ::80%的25%是20岁

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  Example 5
  ::例5

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  What is 5% of 78?
  ::78分的5%是多少?

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  First, convert 5% to a decimal.
  ::首先,将5%转换为小数点。

  $$\begin{array}{r}5\mathrm{\%}=0.05\end{array}$$

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  Next, multiply 78 by 0.05.
  ::下一个乘以78乘以0.05

  $$\begin{array}{r}\begin{array}{rcl}78\times 0.05& =& 3.90\\ x& =& 3.9\end{array}\end{array}$$

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  5% of 78 is 3.9.
  
  ::78人中有5%为3.9人。

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  Review
  ::回顾

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  Find the percent of each number.
  ::找出每个数字的百分率。

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  1. What is 2% of 10?
     ::10分之2%是多少?
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  2. What is 5% of 50?
     ::50的5%是多少?
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  3. What is 10% of 30?
     ::30的10%是多少?
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  4. What is 25% of 18?
     ::18分的25%是多少?
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  5. What is 20% of 36?
     ::36分的20%是多少?
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  6. What is 11% of 40?
     ::40分之11%是多少?
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  7. What is 8% of 80?
     ::80的8%是多少?
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  8. What is 15% of 45?
     ::45分的15%是多少?
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  9. What is 20% of 100?
     ::100的20%是多少?
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  10. What is 25% of 250?
      ::250的25%是多少?
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  11. What is 4% of 60?
      ::60的4%是多少?
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  12. What is 5% of 85?
      ::85的5%是多少?
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  13. What is 2% of 18?
      ::18分的2%是多少?
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  14. What is 15.5% of 90?
      ::90的15.5%是多少?
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  15. What is 20.5% of 70?
      ::70的20.5%是多少?

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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

   

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