PP-T2-DS182

chelseayang

182.

If m and r are two numbers on a number line, what is the value of r ?

(1) The distance between r and 0 is 3 times the distance between m and 0 .

(2) 12 is halfway between m and r.

Ans:E

這題我是這樣解

(1) r=3m

(2) r-12=12-m

(1)(2) r=18 m=6

選C不知那裡錯了

purplebutterfly

 m=-12
r=36

chelseayang

再請教

我有考慮正負問題,但找不到有那對數字可以滿足(1)(2)的條件

能否再請提點

xionghuixhs

要考虑r和m所在正负哪个半轴的问题．

一正一负，和两个都正，答案不同．所以条件无论单独考虑还是综合考虑都不充分．