求助 GWD一题

catherine66

Q26:
K is a set of integers such that if the integer r is in K, then r + 1 is also in K.  Is 100 in K?
(1)      50 is in K.
(2)      150 is in K.
    
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
Answer:
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问题是：为什么条件2不对
谢谢谢谢谢

jtrchina

Well,this Q can be simplified as:K is a set in which every element is at least as great as r.For exemple,if r=1 , then K represents all integers as great as or greater than 1.

the reason that option(2) is dead because the only thing it tells us is that K contains integers>=150.It is still not sure whether 100 is included:100 exsists only if a number<=100 exsists,a premise that we can not properly infer from choice(2).It's out.

catherine66

thanks~

Gongzhe

Well,this Q can be simplified as:K is a set in which every element is at least as great as r.For exemple,if r=1 , then K represents all integers as great as or greater than 1.

the reason that option(2) is dead because the only thing it tells us is that K contains integers>=150.It is still not sure whether 100 is included:100 exsists only if a number<=100 exsists,a premise that we can not properly infer from choice(2).It's out.

-- by 会员 jtrchina (2010/5/5 20:44:44)

可是这道题里面没有给出K的范围呀，如果50就是K里面最大的数，那么也不可以推出100就在K里面啊

locawood

Q26:
K is a set of integers such that if the integer r is in K, then r + 1 is also in K.  Is 100 in K?
(1)      50 is in K.
(2)      150 is in K.
   
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
Answer:
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问题是：为什么条件2不对
谢谢谢谢谢

-- by 会员 catherine66 (2010/5/5 20:21:14)

那么楼主答案是A不？

只要R在R+1就在嘛所以只要比R大的都在~