8.21单利

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  单利

  

  [Figure 1]

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  Kevin has just moved to a new city for a job. He needs furniture but doesn’t have enough money to buy everything he needs. The furniture salesman offers Kevin a store credit card. He can put the cost of the furniture on the card and pay it off over time. The interest  rate  on the card is 15%. Kevin buys $3,000 worth of furniture and puts it on the credit card. How much interest will Kevin pay if it takes him 3 years to pay off the balance?
  ::Kevin刚搬到一个新城市找工作。 他需要家具,但没有足够的钱买他需要的东西。 家具销售员给了Kevin一张商店信用卡。 他可以把家具成本放在卡片上,并在一段时间内付清。 卡片上的利率是15 % 。 Kevin购买了价值3000美元的家具,并将它放在信用卡上。 如果Kevin花3年时间来付清余额,他将支付多少利息?

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  In this concept, you will learn to calculate the simple interest on a  loan .
  ::在此概念中,您将学会计算贷款的简单利息。

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  Calculating Simple Interest
  ::计算简单利息

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  Banks lend people money in the form of a loan. In return, the banks collect interest.  Interest  is the amount of money paid for the use of borrowed money. It is important to calculate the interest before taking a loan.
  ::银行以贷款的形式向人们贷款。作为回报,银行收取利息。利息是用借款支付的数额。在贷款之前计算利息很重要。

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  One way is with simple interest.  Simple interest  is a quick way to calculate the interest of a loan. The  formula  for simple interest is:
  ::一种方法是简单利息。简单利息是计算贷款利息的快速方法。简单利息的公式是:

  $$\begin{array}{r}\begin{array}{rcl}I& =& prt\\ \text{Interest}& =& \text{principal}\times \text{rate}\times \text{time}\end{array}\end{array}$$

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  The  principal  is the sum of money being borrowed.  Interest rate  is the percent of the principal you pay in  addition  to the principal over a time period. Interest rates are usually calculated annually, or per year.  Time  is the amount of time the borrower has agreed to pay back the loan.
  ::本金是借款的金额。利率是您在一段时间内除了本金外还支付的本金的百分率。利率通常是每年或每年计算的。时间是借款人同意偿还贷款的时间。

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

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  Carrie borrowed $500 from the bank. The bank charges a 5% interest rate annually. If it takes Carrie 1 year to pay back the money, how much interest will she pay?
  ::Carrie从银行借了500美元。银行每年收取5%的利率。如果CAR 1 年才能还清这笔钱,她要付多少利息?

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  The principal is $500.
  ::校长是500美元

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  The rate is 5% per year or 0.05.
  ::比率为每年5%或0.05。

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  The time is 1 year.
  ::时间是一年。

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  Let’s use the formula for simple interest.
  ::让我们用这个公式来表达简单的利益。

  $$\begin{array}{r}\begin{array}{rcl}I& =& (500)(0.05)(1)\\ I& =& 25\end{array}\end{array}$$

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  Carrie will pay $25.00 in interest.
  ::Carrie将支付25美元利息

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  Calculate the interest had it taken Carrie 3 years to pay back the loan.
  ::计算如果Carrie花了3年偿还贷款的利息。

  $$\begin{array}{r}\begin{array}{rcl}I& =& (500)(0.05)(3)\\ I& =& (25.00)(3)\\ I& =& \mathrm{\$}75.00\end{array}\end{array}$$

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  Carrie would have paid $75.00 in interest.
  ::Carrie会付75美元利息的

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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 Kevin’s furniture loan.
  ::Kevin的家具贷款有问题,

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  Kevin bought $3,000 worth of furniture and put it on a credit card with a 15% interest rate. He takes 3 years to pay off the loan. To calculate the interest, use the formula:  $\begin{array}{r}I=prt\end{array}$ .
  ::Kevin购买了价值3000美元的家具,并用15%的利率放在信用卡上。他需要3年才能还清贷款。计算利息,使用公式:I = p r t。

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  Substitute  in the given values.
  ::替代给定值。

  $$\begin{array}{r}\begin{array}{rcl}I& =& (3,000)(0.15)(3)\\ I& =& 1,350\end{array}\end{array}$$

   

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  Kevin will pay $1,350 in interest.
  ::凯文将支付1 350美元的利息

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  Example 2
  ::例2

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  Find the simple interest of the loan.
  ::找到贷款的简单利息。

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  Kelly saved $2500.00 in her savings account. Her annual interest rate was 3.5%. In four years, how much interest will Kelly’s account accumulate?
  ::Kelly在储蓄账户中储蓄了2500.00美元。 她的年利率是3.5 % 。 四年后,Kelly的账户将积累多少利息?

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  The principal is $2500.
  ::本金是2500美元

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  The rate is 3.5% per year or 0.035.
  ::比率为每年3.5%或0.035。

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  The time is 4 years.
  ::时间是4年。

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  Use the formula for simple interest.
  ::使用简单利息公式。

  $$\begin{array}{r}\begin{array}{rcl}I& =& prt\\ I& =& (2500)(0.035)(4)\\ I& =& 350\end{array}\end{array}$$

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  Kelly’s account will accumulate $350.00 in interest.
  ::Kelly的账户将累计利息350.00美元。

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  Example 3
  ::例3

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  Mark borrowed $250.00 at 4% for 3 years. How much interest did he pay?
  ::马克在三年里借了250.00美元 4% 他付了多少利息?

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  Use the formula for simple interest.
  ::使用简单利息公式。

  $$\begin{array}{r}\begin{array}{rcl}I& =& prt\\ I& =& (250)(0.04)(3)\\ I& =& 30\end{array}\end{array}$$

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  Mark will pay $30 in interest.
  ::马克将支付30美元的利息。

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  Example 4
  ::例4

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  Kris borrowed $300.00 at 2% for 2 years. How much interest did he pay?
  ::Kris在两年里借了300.00美元,利率为2%,他付了多少利息?

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  Use the formula for simple interest.
  ::使用简单利息公式。

  $$\begin{array}{r}\begin{array}{rcl}I& =& prt\\ I& =& (300)(.02)(2)\\ I& =& 12\end{array}\end{array}$$

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  Kris will pay $12 in interest.
  ::克里斯将支付12美元的利息。

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  Example 5
  ::例5

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  Carmen has $1,200.00 in her savings account at 3% interest. In two years, how much interest will she accumulate?
  ::卡门的储蓄账户里有1200美元,利息为3%。两年后,她将积累多少利息?

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  Use the formula for simple interest.
  ::使用简单利息公式。

  $$\begin{array}{r}\begin{array}{rcl}I& =& prt\\ I& =& (1,200)(0.03)(2)\\ I& =& 72\end{array}\end{array}$$

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  Carmen will pay $72 in interest.
  
  ::卡门将支付72美元的利息

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  Review
  ::回顾

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  Find the simple interest on each amount.
  ::找出每个金额的简单利息。

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  1. $500.00 at 4% for 2 years
     ::两年,500.00美元,按4%计算
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  2. $200.00 at 5% for 3 years
     ::3年200.00美元,按5%计算,为期3年
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  3. $5000.00 at 2% for 2 years
     ::两年,5000.00美元,按2%计算
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  4. $600.00 at 10% for 1 year
     ::600.00美元,按1年10%的10%计算
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  5. $1200.00 at 4% for 2 years
     ::2年1200.00美元,按4%计算,为期2年
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  6. $1500.00 at 3% for 1 year
     ::1500.00美元,按1年3%的3%计算
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  7. $2300.00 at 2% for 2 years
     ::2300.00美元,按两年2%的2%计算
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  8. $500.00 at 4% for 2 years
     ::两年,500.00美元,按4%计算
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  9. $2500.00 at 5% for 5 years
     ::5年5年2500.00美元,按5%计算
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  10. $1500.00 at 11% for 2 years
      ::1500.00美元,按11%计算,两年为11.0%
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  11. $3500 at 3% for 5 years
      ::5年3500美元,3%,5年
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  12. $3500 at 4% for 15 years
      ::15年3500美元,按4%计算,15年
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  13. $13,000 at 4.5% for 6 years
      ::6年13,000美元,按4.5%的4.5%计算
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  14. $23,000 at 3.5% for 10 years
      ::10年,23 000美元,3.5%,为期10年
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  15. $50,000 at 2.5% for 20 years
      ::20年50 000美元,按2.5%计算,20年

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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