6.6查找零件a的比例

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  查找零件a的比例

  

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  Jamal works at a local store after school that sells pumpkin lanterns for $12. The day after Halloween, the store manager wants Jamal to mark down the lanterns by 75%. What new price sticker does Jamal put on them?
  ::Jamal放学后在一家卖南瓜灯的当地商店工作,售价12美元。万圣节后第二天,店经理希望Jamal把灯标上75%。Jamal贴上什么新价格标签?

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  In this concept, you will learn to use a  proportion  to find part  $\begin{array}{r}a\end{array}$ , the amount.
  ::在此概念中,您将学会使用一定比例来找到部分(a),即金额。

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  Proportions to Find the Amount
  ::查找金额的比例

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  Sometimes you will be given the base and the percent, and you will need to find the amount. You can use the same proportion to figure out this missing value,  $\begin{array}{r}a\end{array}$ . You just need to fill in the numbers in the correct places and solve.
  ::有时你会得到基数和百分比, 你需要找到数量。 您可以使用相同的比例来找出这个缺失的值, a 。 您只需要填入正确的位数和解答 。

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  Let’s look at an example.
  ::让我们举个例子。

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  What is 25% of 75?
  ::75的25%是多少?

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  To figure this out, let’s look at what you have been given for information. First, you know the percent so you can fill in that half of the proportion.
  ::为了了解这一点,让我们来看看您所得到的信息。 首先,您知道百分比,所以您可以填入比例的一半。

  $$\begin{array}{r}\frac{25}{100}\end{array}$$

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  Next, you have been given the base. “Of 75” lets you know that this number is the base. The amount is missing. That is our unknown. So the second half of the proportion is:
  ::接下来,您将获得基数。 “ 75 ” 表示您知道这个数字是基数。 数量丢失了。 这是我们未知的。 比例的后半部分是 :

  $$\begin{array}{r}\frac{a}{75}\end{array}$$

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  Now let’s put it together as a proportion and use cross products to solve for  $\begin{array}{r}a\end{array}$ .
  ::现在让我们把它组合成一个比例, 用交叉产品来解决一个问题。

  $$\begin{array}{r}\begin{array}{rcl}\frac{a}{75}& =& \frac{25}{100}\\ 100a& =& 75(25)\\ 100a& =& 1875\\ a& =& 18.75\end{array}\end{array}$$

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  Notice that you moved the decimal point two places to the left when you divided by 100.
  ::注意当除以100时将小数点 2 位移到左边。

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  The answer is 18.75 or  $\begin{array}{r}18\frac{3}{4}\end{array}$  is 25% of 75.
  ::答案是18.75或18 3 4是75的25%。

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  Notice that there isn’t a percent sign here because you were looking for an amount not a percent. Remember to note what you are looking for.
  ::请注意,这里没有百分之一的签名,因为您正在寻找一个不是百分之一的金额。 记住要记住您正在寻找的东西 。

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  Let’s take a look at another example.
  ::让我们看看另一个例子。

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  What number is 15% of 60?
  ::60的15%是多少?

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  First, set up a proportion. Remember, the missing part is  variable   $\begin{array}{r}a\end{array}$ , the amount.
  ::首先,设定一个比例。记住,缺失的部分是变量a, 数额。

  $$\begin{array}{r}\frac{a}{60}=\frac{15}{100}\end{array}$$

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  Next, cross-multiply and solve.
  ::下一个 交叉倍数解决

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 900\\ a& =& 9\end{array}\end{array}$$

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  The answer is 9 is 15% of 60.
  ::答案是 9 是 60 的 15% 。

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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 Jamal and his job at the store.
  ::早些时候,你得到一个问题 关于贾马尔和他的工作 在商店。

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  He needs to put discounted price stickers on the Halloween lanterns. The lanterns, which originally cost $12, are now going to be reduced by 75%. What new price sticker does Jamal put on them?
  ::他需要在万圣节灯笼上贴贴贴贴贴物。 最初花费12美元的灯笼现在将减少75%。 Jamal在灯笼上贴了什么新贴纸?

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  First, if the lanterns are discounted by 75%, their new price is  $\begin{array}{r}100\mathrm{\%}-75\mathrm{\%}\end{array}$  or 25% of the original price.
  ::首先,如果灯笼折扣75%,它们的新价格是100% - 75%或25%的原价。

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  Next, let’s setup the proportion.
  ::接下来,让我们设定比例。

  $$\begin{array}{r}\frac{a}{12}=\frac{25}{100}\end{array}$$

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  Now you can use cross products to solve for the amount.
  ::现在您可以使用交叉产品来解答金额 。

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 25(12)\\ 100a& =& 300\\ a& =& 3\end{array}\end{array}$$

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  The answer is the discounted sticker price Jamal should put on the lanterns is $3.
  ::答案是Jamal应该给灯具贴上3美元的贴贴纸价格。

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  Example 2
  ::例2

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  Mr. Green bought both vegetable and flowering plants for his garden. He bought 40 plants and 35% were flowering plants. How many flowering plants did he buy?
  ::Green先生为花园购买了蔬菜和花卉,他购买了40种植物,35%是花卉。他购买了多少花卉?

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  You can think of this problem as “What is 35% of 40?”
  ::你可以认为这个问题是“40的35%是什么?”

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  40 is the base  $\begin{array}{r}(b)\end{array}$  and 35 is the percent  $\begin{array}{r}(p)\end{array}$ . You need to find the amount  $\begin{array}{r}(a)\end{array}$ .
  ::40是基数(b),35是百分比(p)。您需要找到数额(a) 。

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  First, set up the proportion.
  ::首先,设定比例。

  $$\begin{array}{r}\frac{a}{40}=\frac{35}{100}\end{array}$$

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  Then, use cross products to solve for the amount.
  ::然后,使用交叉产品解决金额问题。

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 35(40)\\ 100a& =& 1,400\\ a& =& 14\end{array}\end{array}$$

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  The answer is Mr. Green bought 14 flowering plants.
  ::答案是Green先生买了14株花卉

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  Example 3
  ::例3

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  What is 20% of 30?
  ::30分的20%是多少?

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  First, let’s set up the proportion.
  ::首先,让我们设定比例。

  $$\begin{array}{r}\frac{a}{30}=\frac{20}{100}\end{array}$$

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  Now you can use cross products to solve for the amount.
  ::现在您可以使用交叉产品来解答金额 。

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 20(30)\\ 100a& =& 600\\ a& =& 6\end{array}\end{array}$$

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  The answer is 6 is 20% of 30.
  ::答案是6是30分的20%

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  Example 4
  ::例4

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  What is 16% of 50?
  ::50的16%是多少?

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  First, let’s set up the proportion.
  ::首先,让我们设定比例。

  $$\begin{array}{r}\frac{a}{50}=\frac{16}{100}\end{array}$$

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  Now you can use cross products to solve for the amount.
  ::现在您可以使用交叉产品来解答金额 。

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 16(50)\\ 100a& =& 80\\ a& =& 8\end{array}\end{array}$$

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  The answer is 8 is 16% of 50.
  ::答案是8是50分的16%。

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  Example 5
  ::例5

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  What is 22% of 80?
  ::80分之22%是多少?

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  First, let’s set up the proportion.
  ::首先,让我们设定比例。

  $$\begin{array}{r}\frac{a}{80}=\frac{22}{100}\end{array}$$

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  Now you can use cross products to solve for the amount.
  ::现在您可以使用交叉产品来解答金额 。

  $$\begin{array}{r}\begin{array}{rcl}100a& =& 22(80)\\ 100a& =& 1,760\\ a& =& 17.6\end{array}\end{array}$$

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  The answer is 17.6 is 22% of 80.
  ::答案是17.6 占80的22%。

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  Review
  ::回顾

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  Find each missing amount.
  ::找出每个失踪的金额

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  1. What number is 25% of 18?
     ::18人中25%是多少?
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  2. What number is 10% of 20?
     ::20的10%是多少?
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  3. What number is 45% of 16?
     ::16人中45%是多少?
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  4. What number is 20% of 44?
     ::44的20%是多少?
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  5. What number is 30% of 100?
     ::100的30%是多少?
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  6. What number is 25% of 60?
     ::60的25%是多少?
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  7. What number is 40% of 80?
     ::80的40%是多少?
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  8. What number is 40% of 60?
     ::60的40%是多少?
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  9. What number is 50% of 120?
     ::120的50%是多少?
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  10. What number is 5% of 12?
      ::12分的5%是多少?
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  11. What number is 5% of 20?
      ::20的5%是多少?
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  12. What number is 16% of 80?
      ::80的16%是多少?
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  13. What number is 25% of 23?
      ::23的25%是多少?
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  14. What number is 50% of 17?
      ::17的50%是多少?
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  15. What number is 30% of 33?
      ::33的30%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