扫描二维码，直接登录
题库 / Prep2007E1-DS-42
John and Mary own shares of stock in a certain company. Does John own more shares of the company's stock than Mary?
(1) Mary owns more than 500 shares of the company's stock.
(2) The number of shares of the company's stock that John owns is 400 less than twice the number of shares of the company's stock that Mary owns.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
(1) M>500
(2) J = 2M-400
(1)－(2) J-M= M-400>100
=> 注意不需要完全带入 要了解列式的目的
Question: is J>M?
(1) Mary owns more than 500 shares of the company's stock --> M>500. Clearly insufficient, since no info about J.
(2) --> J=2M-400 --> substitute J in the question --> question becomes: "is 2M-400>M?" --> "is M>400?" We don't know that. Not sufficient.
(1)+(2) From (2) the question became "is M>400?" and (1) says that M>500, thus the answer to the question is YES. Sufficient.
做差比较
1）M>500
2）J = 2M-400
1）－2） J-M= M-400>100
原来不等式也可以互相加减玩阿
(1)M>500==>NS
(2)J=2M-400==>J-M=M-400>0==>J>M==>s
总结：遇到比较大小题目可以看能不能做差比较>0 or
问J>M?
1. M>500 单独不行
2. J = 2M-400 单独也不行
1+2： J=2M-400, J-M=M-400; 又M>500, M-400>0, 所以J-M>0, J>m
问J>M?
1. M>500 单独不行
2. J = 2M-400 单独也不行
1+2： J=2M-400, J-M=M-400; 又M>500, M-400>0, 所以J-M>0, J>m
J,M都拥有一个公司的股票，问J有的股票大于M？J-M>0?
条件1：M>500 不知道J的情况，insufficient
条件2：2M-400=J 不知道 JM insufficient
条件1+条件2： 2M-400=J 两遍同减去M(同时减去m，）
m-400=j-m M>500 J-M= M-400>100 J>M SUFFICIENT
选C