一月JJNO163核对

寂寞的自由

163.    两种测量工具是成比例,用来测一个东西, 分别为24和60,相处另一个东西为30和90,(NOT CLEAR), 问测出100时,另一个测出多少.
自由的答案： 没通过！感觉题目出错了！

binneal

没错，就是不清楚。24 of system A can be maped to 30 of B, 60 of A can be mapped to 90 of B, asking what can 100 of A be mapped to of B.
Solution: (100-24)/(60-24) = (x-30)/(90-30)

寂寞的自由

以下是引用binneal在2004-1-21 13:05:00的发言：
没错，就是不清楚。24 of system A can be maped to 30 of B, 60 of A can be mapped to 90 of B, asking what can 100 of A be mapped to of B.
Solution: (100-24)/(60-24) = (x-30)/(90-30)

黑体字，自由没看懂！！！ 笨的我想哭~~~~~
另外下面这个题好象同上面的那个题是一样的。
168. 这道题巨长, 阅读要仔细, 题目并不难.
有R和S两个measure系统, 测量同样的东东, R系统得出的值6和24分别对应于S系统中的30和60, R和S系统成线性关系, 问题: 如果另一个东东用S系统测得100, R系统测得的值是多少?
作者答案及思路：答案:48

什么叫做成线性关系？大家帮帮笨笨的自由，谢谢

chenholan

48

groundkeeper

(24-6)/(60-30)=(X-24)/(100-60)......X=48

寂寞的自由

以下是引用groundkeeper在2004-1-21 19:02:00的发言：
(24-6)/(60-30)=(X-24)/(100-60)......X=48

谢谢您，可是，自由想问一下，您列的这个式子和线性关系之间是什么关系呢？自由想确切明白什么叫做线性关系，这样的话，就明白了作题的灵魂是什么，而且也为GMAT通过后的读书做准备，谢谢大家帮忙自由！！！

zida

When two variables are perfectly linearly related, the points of a scatterplot fall on a straight line. If you know the score of a subject on one variable then you can determine the score on the other variable exactly. For instance, y=cx+c, c denotes any constant number, is a linear relationship equation. Such y=5x+2, or y=17x+200, or the like.  From our case, we know that:
30=k24+c
90=k60+c, so, it can be found k=5/3 and c= -10
Hence, the equation is y=(5/3)x -10
Let’s check:
X=24   => y=(5/3)*24-10=30
X=60   => y=(5/3)*60-10=90
X=100 => y=(5/3)*100-10=470/3
But, if the question asks in this way: if 6=>30, 24=>60 what’s x=>100?
Similar, from
30=k6+c
60=k24+c,    we have k=5/3 and c=20, so
X=6    => y=(5/3)*6 + 20 =30
X=24  => y=(5/3)*24 +20=60
x=?    100=(5/3)*x +20 => x=48
By the way, (100-24)/(60-24) = (x-30)/(90-30) => x=470/3

daidai11

(90-60)/(30-24)=(x-60)/(100-24)