Course: 5.4 查找一个数字的百分率

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查找一个数字的百分率
Juno works at Wild Adventure amusement park, which has an average of 30,000 visits daily. Over 75% of those people ride on the park’s biggest roller coaster, The Zeus. How can Juno figure out how many people ride The Zeus?
::朱诺在野外冒险游乐园工作,该公园每天平均有30,000次访问。超过75%的人乘坐该公园最大的过山车“宙斯 ” ( The Zeus ) 。朱诺如何知道有多少人骑着“宙斯 ” ( Zeus ) ?

In this concept, you will learn to find the percent of a number using multiplication.
::在此概念中, 您将学会使用乘法来找到一个数字的百分率。

Percent of a Number
::数字的百分率

Part of the usefulness of percent is being able to find percentages of a number. In other words, if you are planning a barbecue and the butcher tells you that 30% of the people want chicken you can use this percent to find how many people will be eating chicken. For how many people should you buy chicken?
::百分比的用处部分在于能够找到一个数字的百分率。换句话说, 如果您在计划烧烤, 屠夫告诉你, 30%的人想要鸡, 你可以用这个百分率来找到有多少人会吃鸡。对于多少人,你应该买鸡?

The key words here are “of a number” this means that you multiply to solve the problem. You can convert the percent to a decimal and multiply or convert it to a fraction and multiply.
::这里的关键词是“ 数字中的” , 这意味着您会乘以解决问题。您可以将百分比转换为小数点, 然后乘以, 或者将其转换为分数和倍数。

Let’s suppose that you invited 58 people to the barbecue. If 30% prefer chicken, then you need to know how many people that is.
::假设你邀请了58人参加烧烤。如果30%的人更喜欢鸡肉,那么你就需要知道有多少人。

First, convert 30% to either a decimal or a fraction.
::首先,将30%转换为小数点或分数。

$\begin{aligned} \begin{array}{rcl} 30 % = \frac{30}{100} or 30 % = 0.30 \\ 30 % = \frac{3}{10} \end{array} \end{aligned}$
$\begin{align*}\begin{array}{rcl} && 30\% = \frac{30}{100} \quad \text{or} \quad 30\% = 0.30 \\ \\ && 30\% = \frac{3}{10} \end{array}\end{align*}$
::30300030 3030 310

Next, use the decimal or the fraction to multiply by the number of people you invited.
::接下来,使用小数点或分数乘以您邀请的人数。

$\begin{aligned} \begin{array}{rcl} \frac{3}{10} \times 58 = \frac{174}{10} or 0.3 \times 58 = 17.4 \\ \frac{3}{10} \times 58 = 17.4 \end{array} \end{aligned}$
$\begin{align*}\begin{array}{rcl} && \frac{3}{10} \times 58 = \frac{174}{10} \quad \text{or} \quad 0.3 \times 58 = 17.4 \\ && \frac{3}{10} \times 58 = 17.4 \end{array}\end{align*}$
::310x58=17.4

The answer is 17.4.
::答案是17.4。

Therefore about 17 people want chicken at the barbecue.
::所以大约17个人想在烧烤会上吃鸡肉

Examples
::实例

Example 1
::例1

Earlier, you were given a problem about Juno at Wild Adventure.
::早些时候,你在野外冒险时遇到朱诺的问题

You need to find the number of people that go on the roller coaster per day. You know that 75% of the people going to the amusement park go on this ride. You also know that there were about 30,000 people at the park on any given day.
::您需要找到每天坐过山车的人数。您知道有75%的人去游乐园。您也知道在任何一天公园里都有大约30,000人。

First, change the percent to a decimal.
::首先,将百分比改为小数点后一位。

$\begin{aligned} 75 % = 0.75 \end{aligned}$
$\begin{align*}75\% = 0.75\end{align*}$

Next, multiply 30,000 by the decimal.
::接下来,乘以3万乘以小数点

$\begin{aligned} 0.75 \times 30000 = 22500 \end{aligned}$
$\begin{align*}0.75 \times 30000 = 22500\end{align*}$

The answer is 22500.
::答案是22500

Therefore, approximately 22,500 people go on Wild Adventure’s biggest roller coaster, The Zeus, each day.
::因此,每天约有22 500人上野外冒险最大的过山车《宙斯》。

Example 2
::例2

A survey states that 15% of the people surveyed like olives. Out of the 500 people surveyed, about how many like olives?
::调查显示,15%的被调查者喜欢橄榄。在500名被调查者中,有多少人喜欢橄榄?

First, write a statement describing the problem.
::首先,写一个说明问题的声明。

$\begin{aligned} 15 % of 500 \end{aligned}$
$\begin{align*}15\% \ \text{of} \ 500\end{align*}$
::占500人15%的15%

Next, change the percent to a decimal.
::接下来,将百分比改为小数点后一位。

$\begin{aligned} 15 % = 0.15 \end{aligned}$
$\begin{align*}15\% = 0.15\end{align*}$

Then, multiply the number of people by the decimal.
::然后,将人数乘以小数点。

$\begin{aligned} 0.15 \times 500 = 75 \end{aligned}$
$\begin{align*}0.15 \times 500 = 75\end{align*}$

The answer is 75.
::答案是75

Therefore 75 of the 500 people like olives.
::因此,500人中有75人喜欢橄榄。

Example 3
::例3

What is 20% of 18?
::18分的20%是多少?

First, change the percent to a decimal.
::首先,将百分比改为小数点后一位。

$\begin{aligned} 20 % = 0.20 \end{aligned}$
$\begin{align*}20\% = 0.20\end{align*}$

Next, multiply 18 by the decimal.
::下一个乘以18乘以小数。

$\begin{aligned} 0.20 \times 18 = 3.6 \end{aligned}$
$\begin{align*}0.20 \times 18 = 3.6\end{align*}$

The answer is 3.6.
::答案是3.6。

Example 4
::例4

What is 25% of 40?
::40分的25%是多少?

First, change the percent to a decimal.
::首先,将百分比改为小数点后一位。

$\begin{aligned} 25 % = 0.25 \end{aligned}$
$\begin{align*}25\% = 0.25\end{align*}$

Next, multiply 40 by the decimal.
::下一个乘以40乘以小数点

$\begin{aligned} 0.25 \times 40 = 10 \end{aligned}$
$\begin{align*}0.25 \times 40 = 10\end{align*}$

The answer is 10.
::答案是10个

Example 5
::例5

What is 5% of 80?
::80的5%是多少?

First, change the percent to a decimal.
::首先,将百分比改为小数点后一位。

$\begin{aligned} 5 % = 0.05 \end{aligned}$
$\begin{align*}5\% = 0.05\end{align*}$

Next, multiply 80 by the decimal.
::下一个乘以80乘以小数。

$\begin{aligned} 0.05 \times 80 = 4 \end{aligned}$
$\begin{align*}0.05 \times 80 = 4\end{align*}$

The answer is 4.
::答案是4。

Review
::回顾

Find the percent of the given number by converting the percent to a decimal. You may round if necessary.
::通过将百分数转换为小数小数来查找给定数字的百分率。必要时您可以四舍五入。

1. 30% of 90
::1. 90%的30%

2. 3% of 12
::2. 占12的3%

3. 14% of 900
::3. 占900人14%

4. 33% of 99
::4. 99人中的33%

5. 18% of 100
::5. 占100的18%

6. 8% of 72
::6. 72人中的8%

7. 11% of 50
::占50的7% 11%

8. 14.5% of 30
::8. 占30人总数的14.5%

9. 12% of 80
::9. 占80人中的12%

10. 2% of 800
::10. 占800人2%

11. 150% of 21
::11. 占21人总数的150%

12. 45% of 60
::12. 占60人总数的45%

Read the following situations carefully and answer the questions accordingly.
::仔细阅读下列情况,并相应回答问题。

13. For every paycheck you receive, your employer pays 6% to social security. Write this percent as a ratio with a denominator of 100.
::13. 雇主为每领取一次工资支付6%的社会保障金,用人单位支付6%的社会保障金,以100分位数的比例写成这一百分比。

14. What is 30% of 500?
::500的30%是多少?

15. A store did a survey and found that $\begin{align*}\frac{4}{5}\end{align*}$ of its customers have shopped at its competitors’ stores within in the previous month. What percent is that?
::15. 一家商店进行了一项调查,发现45名顾客在上个月内在其竞争对手的商店购物。

Review (Answers)
::回顾(答复)

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。

Section outline

General

查找一个数字的百分率

Percent of a Number ::数字的百分率

Examples ::实例

Example 1 ::例1

Example 2 ::例2

Example 3 ::例3

Example 4 ::例4

Example 5 ::例5

Review ::回顾

Review (Answers) ::回顾(答复)

Percent of a Number
::数字的百分率

Examples
::实例

Example 1
::例1

Example 2
::例2

Example 3
::例3

Example 4
::例4

Example 5
::例5

Review
::回顾

Review (Answers)
::回顾(答复)