一道PREP上的题~~牛想不通~~~

xionghuixh

r和m是数轴上的两个数，问r的大小

1 the distance between m and 0 are 3 times the distance between m and 0

2 12 is the halfway between m and r

我选了C~~答案是E~~~我想来想去觉得是C丫~~~

Redshoe08

QUOTE:

以下是引用xionghuixh在2009-6-26 6:57:00的发言：

r和m是数轴上的两个数，问r的大小

1 the distance between m and 0 are 3 times the distance between m and 0

2 12 is the halfway between m and r

我选了C~~答案是E~~~我想来想去觉得是C丫~~~

 

此主题相关图片如下：

plmnpler

QUOTE:

以下是引用xionghuixh在2009-6-26 6:57:00的发言：

r和m是数轴上的两个数，问r的大小

1 the distance between m and 0 are 3 times the distance between m and 0

2 12 is the halfway between m and r

我选了C~~答案是E~~~我想来想去觉得是C丫~~~

条件1 是是写错了呀 我暂且当做 r 到 0 的距离是 m 到0 的距离的三倍来做

情况一 m >0  r >0

           则有（1）3m=r （2） r-12=12-m  --> m=6 r=18

情况二 m < 0 r >0

          则有（1）3m=r   （2）m+12=r-12 --> m=-12 r=36

所以，r有两个取值。不唯一。故E。

BruceNornia

题目也很奇怪 少敲了好几个字

楼主的条件1很模糊....写错了...我们假设是  the distance between m and 0 is 3 times the distance between r and 0

 

条件 1： |m| = 3|r|

条件 2：  m+r=24

 

上述方程有两组解答： m=18 r=6; 或者 m=36 r=-12