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楼主
发表于 2012-3-4 19:00:40 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly.Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively.What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?



A.20

B.36

C.48

D.60

E.84
related linearly 指什麼?? 這條答案是 48. 如何計算?
謝謝大家!
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沙发
发表于 2012-3-4 19:03:37 | 只看该作者
C. 48
Since the R-scale and S-scale are related linearly, you'll want to find a linear equation to correlate the two values.

Let value on R-scale = x and value on S-scale = y to give the points (6, 30) and (24, 60).

Since you have two points you can find the slope of the line connecting them. Slope formula: (y2 - y1) / (x2 - x1)

(60 - 30) / (24 - 6)
= 30/18
= 5/3

Now that you have the slope you can use the point-slope form of a linear equation: y - y1 = m(x - x1) where m = slope. Plug in either point, doesn't matter, I used (24, 60):

y - 60 = 5/3(x - 24)
y = (5/3)x - 40 + 60
y = (5/3)x + 20 <-- your equation

Now that you have the equation, plug in 100 for y since 100 is the S-scale value you want to find:

(5/3)x + 20 = 100
(5/3) x = 80
x = 48

So, the R-scale value is 48, or answer C.  

Source: http://askville.amazon.com/quantity-measured-scales-R-scale-S-scale-related-linearly-Details/AnswerViewer.do?requestId=2562719
板凳
 楼主| 发表于 2012-3-4 19:11:42 | 只看该作者
什麼!!!!!!!!!!!!!!!!!!!! 這麼長!!!!!!!!
十分十分多謝你的幫助!
我會好好看清楚!
感激!!
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