用合理数字解决多步问题

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In This Lesson
::在本课程中

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Y ou will use fractions, decimals, and percents in real-world situations. Sometimes, it may be easier to use a decimal instead of a fraction and vise versa. To change a percent into a decimal, you need to move the decimal point two places to the left. To change a decimal to a percent, you will move the decimal point two places to the right and add the percent symbol.
::在现实世界中,您将使用分数、小数和百分比。有时,使用小数而不是分数比较容易,反之则比较容易。要将一个百分数变为小数,您需要将小数点二移到左边。要将小数点二移到一个百分数,您将把小数点二移到右边,并添加百分数符号。

  

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Shopping Discounts
::购物折扣

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A local appliance store, Fiddler's, is having a Memorial Day sale where all the appliances are 10% off. In addition , if you get their credit card, you will get an additional 15% off your first purchase. If a washing machine is $800 normally, how much will it be on Memorial Day and with the new credit card?
::本地家用电器商店“小提琴手”正在举行纪念日销售,所有家用电器都停产10%。此外,如果你拿到信用卡,第一次购买后还会得到15%的额外收入。如果洗衣机通常为800美元,那么在纪念日和新信用卡上要花多少钱?

 

 

 

 

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Discussion Question
::讨论问题

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Why do you think that retailers do one percentage, then the other when discounting an item? Why don’t they add the percentages, then take the discount?
::为什么你认为零售商只做一个百分比,而在打折时做另一个百分比? 他们为什么不加上百分比,然后打折扣呢?

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Notice that the percent paid, as a decimal, is 1 − (percent off). This makes sense because 1 is like the whole or full price of an item. Reversely, 1 −  (percent paid) is the same as the percent off, as a decimal.
::请注意,按小数点计算,支付的百分比为 1 - (减幅百分比) 。 这有道理, 因为 1 和 项目的整价或全价一样。 反之, 1 - (减幅百分比)和 减幅百分比相同, 与小数点相同 。

 

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Skatepark
::滑雪公园

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A new skatepark, Sk8er L8er, is putting in two kickers with a grind box in the middle, like the picture. To make the feature ready to skate on, the skatepark must also put a layer of Skatelite over the surface to make it smooth and perfect for tricks. The skatepark needs to figure out how many linear feet of Skatelite to buy for this feature. The ramp on each kicker is $\begin{array}{r}x\end{array}$  feet long, and the grind box is  $\begin{array}{r}\frac{3}{4}x\end{array}$  feet long. The height is  $\begin{array}{r}\frac{1}{2}x\end{array}$  feet.
::一个新的滑板场, SK8er L8er, 正在把两只脚踢进两只脚, 中间有一个磨碎的盒子, 就像照片一样。 要让这个功能可以滑冰, 滑板场还必须在表面放上一层滑板, 以便滑滑滑和完美。 滑板场需要弄清楚要为这个特性买几英尺的滑板。 每个脚板的斜坡是x英尺长的, 磨碎盒是34英尺长的。 高度是12英尺高 。

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Use the interactive to  create the feature to the specifications above.
::使用互动来创建上述规格的特性。

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• Adjust the blue and green dots on the corners of each kicker and grinder to fit the measurements.
  ::调整每个踢踏机和研磨机角的蓝色和绿色点,以适应测量。
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• Each kicker is a right triangle, and the grinder is a rectangle.
  ::每个踢球机都是右三角形 研磨机是矩形
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• The entire feature will be 4 feet wide.
  ::整个地貌将宽四英尺

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In terms of $\begin{array}{r}x,\end{array}$  how many linear feet of Skatelite is needed?
::就x而言,需要多少条Skatelite线性英尺?

 

 

 

 

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Discussion Question
::讨论问题

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Go back to the original dimensions of $\begin{array}{r}x,\frac{3}{4}x,\end{array}$  and $\begin{array}{r}x.\end{array}$  Discuss with your classmates what values of $\begin{array}{r}x\end{array}$  make sense, and what values do not. Would you consider the overall size of the skatepark? Or, the cost of the Skatelite? (It is about $6.50 a linear foot)
::回到 x, 34x 和 x 的原始维度。 与您的同学讨论 x 值有什么意义, 哪些值没有意义 。 您考虑滑板场的总体大小吗 ? 或者, Skatelite 的成本 ? (每直径约6. 50美元)