一些逻辑问题的分析

aomeisoft7 · 发表于 2010-9-22 14:58:32

帖子里有一些问题的以及个人解答

祝大家都取得好成绩

bdsjb116 · 发表于 2010-9-22 16:13:19

先问lz两题，刚刚做错的...prep破解版里面的

第一题

19. (27788-!-item-!-188;#058&003653)
With a record number of new companies starting up in Derderia and with previously established companies adding many jobs, a record number of new jobs were created last year in the Derderian economy. This year, previously established companies will not be adding as many new jobs overall as such companies added last year. Therefore, unless a record number of companies start up this year, Derderia will not break its record for new jobs created.
Which of the following is an assumption on which the argument relies?
(A) Each year, new companies starting up create more new jobs overall than do previously established companies.
(B) Companies established last year will not add a greater number of jobs overall this year than they did last year.
(C) This year, the new companies starting up will not provide substantially more jobs per company than did new companies last year.
(D) This year, the overall number of jobs created by previously established companies will be less than the overall number of jobs lost at those companies.
(E) The number of jobs created in the Derderian economy last year was substantially larger than the number of jobs lost last year.

答案是C，为什么A不对
------------------------------------------
第二题
24. (28903-!-item-!-188;#058&004064)
Although exposure to asbestos is the primary cause of mesothelioma, a slow-developing cancer, researchers believe that infection by the SV40 virus is a contributing cause, since in the United States 60 percent of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40. SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus. Researchers hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.
Which of the following, if true, most strongly supports the researchers' hypothesis?
(A) SV40 is widely used as a research tool in cancer laboratories.
(B) Changes in the technique of manufacturing the vaccine now prevent contamination with SV40.
(C) Recently discovered samples of the vaccine dating from 1960 still show traces of the virus.
(D) In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
(E) In Finland, where the polio vaccine was never contaminated, samples from mesotheliomas do not contain SV40.

答案是E，为什么不是C？

aomeisoft7 · 发表于 2010-9-22 20:22:14

先问lz两题，刚刚做错的...prep破解版里面的

第一题

19. (27788-!-item-!-188;#058&003653)
With a record number of new companies starting up in Derderia and with previously established companies adding many jobs, a record number of new jobs were created last year in the Derderian economy. This year, previously established companies will not be adding as many new jobs overall as such companies added last year. Therefore, unless a record number of companies start up this year, Derderia will not break its record for new jobs created.
Which of the following is an assumption on which the argument relies?
(A) Each year, new companies starting up create more new jobs overall than do previously established companies.
(B) Companies established last year will not add a greater number of jobs overall this year than they did last year.
(C) This year, the new companies starting up will not provide substantially more jobs per company than did new companies last year.
(D) This year, the overall number of jobs created by previously established companies will be less than the overall number of jobs lost at those companies.
(E) The number of jobs created in the Derderian economy last year was substantially larger than the number of jobs lost last year.

答案是C，为什么A不对

-- by 会员 bdsjb116 (2010/9/22 16:13:19)

增加的工作 = 新公司提供的工作(平均每个公司提供的工作*公司数)+ 老公司提供的工作

今年老公司提供的工作 < 去年老公司提供的工作
结论：除非,今年新公司数目 >去年新公司数目，今年增加的工作才会比去年增加的多
求假设
C 其假设是平均每个公司提供的工作没有增加
取非。我们假设每个公司提供的工作增加了，那么不用增加公司数目，就可以提供很多工作了，削弱结论
A 每年，新公司提供的工作比老公司提供的工作更多。这个是无关项。

aomeisoft7 · 发表于 2010-9-22 20:49:02

第二题
24. (28903-!-item-!-188;#058&004064)
Although exposure to asbestos is the primary cause of mesothelioma, a slow-developing cancer, researchers believe that infection by the SV40 virus is a contributing cause, since in the United States 60 percent of tissue samples from mesotheliomas, but none from healthy tissue, contain SV40. SV40 is a monkey virus; however, in 1960 some polio vaccine was contaminated with the virus. Researchers hypothesize that this vaccine was the source of the virus found in mesotheliomas decades later.
Which of the following, if true, most strongly supports the researchers' hypothesis?
(A) SV40 is widely used as a research tool in cancer laboratories.
(B) Changes in the technique of manufacturing the vaccine now prevent contamination with SV40.
(C) Recently discovered samples of the vaccine dating from 1960 still show traces of the virus.
(D) In a small percentage of cases of mesothelioma, there is no history of exposure to asbestos.
(E) In Finland, where the polio vaccine was never contaminated, samples from mesotheliomas do not contain SV40.

答案是E，为什么不是C？

-- by 会员 bdsjb116 (2010/9/22 16:13:19)

尽管exposure to asbestos 是mesothelioma 原因之一，学者认为，SV40病毒也是一个原因。因为调查发现60% 的患者有SV病毒。1960年，polio疫苗感染了SV40病毒。所以学者认为含有病毒的polio疫苗，是mesothelioma里面有SV40的原因。

简单点，感染SV40病毒的polio疫苗 > 导致mesothelio含有SV40
求支持
E 在芬兰，Polio疫苗没有感染SV40，那里的mesothelioma患者不含有SV 40
支持了结论
C 现在发现的1960年的polio疫苗样本里有SV40（就是原题的一个条件，不能支持或削弱结论）
觉得这种支持一种因果结论的题型，选项里必然会有这一因（polio）一果（mesothelioma）的关键词，否则不能说明2者关系

bdsjb116 · 发表于 2010-9-22 21:38:30

先谢谢ls

第一题我明白了，当时直接把A取非带进去感觉结论不对就选了。没仔细看后面的。

第二题后来一想这就是个逆否命题。
hypotheis的内容是 this vaccine was the source of the virus found in mesotheliomas decades later
疫苗是1960年之后发现的m病毒缘由。这是在说1960之后只要有m就必然是v感染的。所以逆否的话：没感染v就没有m，所以E是加强。

不过捎带问个我当时做错的判断：hypotheis的说的“later"，所以我认为这件事要成立的条件是时间在1960之后，请问E并没有说时间，可不可以认为在1960之前这种hypotheis是不成立的呢？

aomeisoft7 · 发表于 2010-9-22 22:13:52

先谢谢ls

第一题我明白了，当时直接把A取非带进去感觉结论不对就选了。没仔细看后面的。

第二题后来一想这就是个逆否命题。
hypotheis的内容是 this vaccine was the source of the virus found in mesotheliomas decades later
疫苗是1960年之后发现的m病毒缘由。这是在说1960之后只要有m就必然是v感染的。所以逆否的话：没感染v就没有m，所以E是加强。

不过捎带问个我当时做错的判断：hypotheis的说的“later"，所以我认为这件事要成立的条件是时间在1960之后，请问E并没有说时间，可不可以认为在1960之前这种hypotheis是不成立的呢？

-- by 会员 bdsjb116 (2010/9/22 21:38:30)

1960前就不存在这种假设了。因为1960年vaccine没有感染，所以患者身体里也不会有vs40。
题目的逻辑是：
vaccine 感染了 >　患者身体里就有vs40
vaccine没感染 > 患者身体里就没有vs40
由此确定，这个vs40是感染的vaccine引起的
和时间其实没有关系

除非问“削弱”时可用到这样的选项：
"1960年前，vaccine没有感染，可发现患者身体里也有vs40" （说明不是vaccine感染的原因）

天使追梦 · 发表于 2010-9-22 23:03:29

周末考试，帮忙呀~~
1、http://forum.chasedream.com/GMAT_CR/thread-485758-1-1.html
2、http://forum.chasedream.com/GMAT_CR/thread-485757-1-1.html
拜托啦~（回在我的帖子里行吗？这样我这有提示~）thx~

aomeisoft7 · 发表于 2010-9-23 00:14:33

周末考试，帮忙呀~~
1、http://forum.chasedream.com/GMAT_CR/thread-485758-1-1.html
2、http://forum.chasedream.com/GMAT_CR/thread-485757-1-1.html
拜托啦~（回在我的帖子里行吗？这样我这有提示~）thx~

-- by 会员天使追梦 (2010/9/22 23:03:29)

已经回答啦！~

fannybeibei · 发表于 2010-9-23 10:41:06

lz 有空看一下吧http://forum.chasedream.com/GMAT_CR/thread-485743-1-1.html
先行谢过了～～～

aomeisoft7 · 发表于 2010-9-23 12:31:24

lz 有空看一下吧http://forum.chasedream.com/GMAT_CR/thread-485743-1-1.html
先行谢过了～～～

-- by 会员 fannybeibei (2010/9/23 10:41:06)

已回复~~

一些逻辑问题的分析

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