犇犇奉献，逻辑几类题型的见解和思录，持续更新中~

犇犇

犇犇咨询团成立以来也有半年了，答过疑，教过考生，做过jj讨论稿，以后会不定期的发布一些gmat的逻辑见解和思路，望指教~
以后的帖子会按照削弱、加强、假设、评价、归纳、解释、填空、黑脸的顺序来一类类更新，敬请关注，有问题大家也可以一起讨论

人在美国，暂时没时间更新
有问题可以加qq，303932934，尽力帮大家解决

请关注持续更新的数学资料大奉献：http://forum.chasedream.com/GMAT_Math/thread-560874-1-1.html 谢谢犇犇-【肛裂】同学


这个是以后当月的gmat数学狗狗讨论群：136480565  
加的同学注明cder and 考试日期，学术群，切勿太水~


OG12中的削弱题：1、5、15、23、30、35、36、40、45、60、63、73、75、83、87、90、81、88、96、104、111、114、116、118、120、123



下面选取几道，个人觉得有代表性的削弱题先举例说明，然后总结一下



OG12第23题

A drug that is highly effective in treating many types of infection can, at present, be obtained only from the bark of the ibora, a tree that is quite rare in the wild. It takes the bark of 5,000 trees to make one kilogram of the drug. It follows, therefore, that continued production of the drug must inevitably lead to the ibora’s extinction.

Which of the following, if true, most seriously weakens the argument above?


1.先不看选项，来看题干。做逻辑题首先要看问题，看看问题中有用的信息。这一题，问题只能说明本道题问的是削弱。那么，看到weaken这个字眼出现，知道了是削弱题，脑海中立马要反应过来，题干的结论是错的（虽然说得有点儿绝对化，但是目的是反驳这个argument，那就干脆认为这个argument的最终结果是错的），然后找漏洞进行反驳。至于这个叙述方式到底是什么，我个人觉得不需要太多关注，不管是因果型、条件型、类比型还是调查，最关键的是发现题目的漏洞，这个时候逻辑链就能派上用场了。

咳咳，废话说了很多，进入正题，看看题干的结论到底是什么

2.Therefore点出了结论：continued production of the drug must inevitably lead to the ibora’s extinction. 看到结论直接默认，持续的drug生产不会导致ibora灭绝。

3.找到了结论，那么看这个题干是如何推理出结论的，也就是逻辑链。

生产1kg某种drug需要5000棵稀有的wild ibora为原料à持续的drug生产则ibora灭绝

4.得出了逻辑链，就可以推测问题的源头了

从后往前倒推：持续的drug生产不会导致ibora灭绝à原料不仅限于wild ibora。

5.再看答案，呼之欲出啊了。

(A) The drug made from ibora bark is dispensed to doctors from a central authority.

(B) The drug made from ibora bark is expensive to produce.

(C) The leaves of the ibora are used in a number of medical products.

(D)The ibora can be propagated from cuttings and grown under cultivation. D

(E) The ibora generally grows in largely inaccessible places.

关于E选项为什么错。个人感觉因为是continued production意思就是已然在生产了，和能不能取得无关了。

再则，大家寻思一下，如果这道题目变成assumption呢？答案是什么呢？



OG12第30题

Robot satellites relay important communications and identify weather patterns. Because the satellites can be repaired only in orbit, astronauts are needed to repair them. Without repairs, the satellites would eventually malfunction. Therefore, space flights carrying astronauts must continue.

Which of the following, if true, would most seriously weaken the argument above


我的思考过程：

1.看问题，削弱，无其他关键信息

2.找结论：space flights carrying astronauts must continue

3.将结论否定之：space flights carrying astronauts may not continue

4.逻辑链：satellites只能在轨道上修理不修就坏了à astronauts are neededà space flights carrying astronauts must continue

5.反推：space flights carrying astronauts may not continueà astronauts are not needed

6.找到最终需要反驳的源头了：astronauts are not needed，找个理由说明为什么astronaut不需要呗。

7.找答案↓

(A) Satellites falling from orbit because of malfunctions burn up in the atmosphere.

(B) Although satellites are indispensable in the identification of weather patterns, weather forecasters also make some use of computer projections to identify weather patterns.

(C) The government, responding to public pressure,has decided to cut the budget for space flights and put more money into social welfare programs.

(D) Repair of satellites requires heavy equipment, which adds to the amount of fuel needed to lift a spaceship carrying astronauts into orbit.

(E) Technical obsolescence of robot satellites makes repairing them more costly and less practical than sending new, improved satellites into orbit.



OG12第40题

In the last decade there has been a significant decrease in coffee consumption. During this same time, there has been increasing publicity about the adverse long-term effects on health of the caffeine in coffee. Therefore, the decrease in coffee consumption must have been caused by consumers’ awareness of the harmful effects of caffeine.

Which of the following, if true, most seriously calls into question the explanation above?


1.看问题，削弱，没有其他关键信息

2.找结论：the decrease in coffee consumption must have been caused by consumers’ awareness of the harmful effects of caffeine.

3.否定结论：the decrease in coffee consumption may not have been caused by consumers’ awareness of the harmful effects of caffeine.

4.逻辑链：increasing publicity about the adverse long-term effects on health of the caffeine in coffeeàconsumers’ awareness of the harmful effects of caffeineàdecrease in coffee consumption

5.反推，其实这一题不需要反推，很容易，甚至连逻辑链都不需要推，既然否定完结论后出现的结果是：the decrease in coffee consumption may not have been caused by consumers’ awareness of the harmful effects of caffeine，那就必然寻找他因了。找到别的原因说明the decrease in coffee consumption咯。

6.寻找他因↓

(A) On average, people consume 30 percent less coffee today than they did 10 years ago.

(B) Heavy coffee drinkers may have mild withdrawal symptoms, such as headaches, for a day or so after significantly decreasing their coffee consumption.

(C) Sales of specialty types of coffee have held steady as sales of regular brands have declined.

(D) The consumption of fruit juices and caffeine-free herbal teas has increased over the past decade.

(E)Coffee prices increased steadily in the past decade because of unusually severe frosts in coffee-growing nations.

再次，请大家看看，哪一个选项是支持结论的答案呢？



总结

整体的做题过程就是：1. 看问题，注意题型，有没有关键信息

2. 找结论

3. 自动否定找到的结论

4. 推理逻辑链

5. 用否定的结论反推，找到出问题的源头，也就是weaken point

6. 找到了weaken的点，看选项



PS：其实逻辑题对于阅读的理解还有思维过程有很高的要求，可以说，sc经过大量的做题和总结、归纳之后可以很快的提高；rc考的是阅读速度和快读的理解，和平时积累不可分割，同时机经帮助较大。而对于逻辑来说，要是基础不行，读不懂题，自然悲剧；读懂了题，找不到突破点，同样容易悲剧，这是思维过程的出现问题；同时，逻辑的机经是双刃剑，没有一个正确思维的同学，看了逻辑机经最终只会顾着背答案，考试容易迷糊，逻辑寂静需要自己思考整理，最好把完整的寂静都推理一下逻辑链，思考一下答案方向。

GWD30-Q32
A major chemical spill occurred five years ago at Baker’s Beach, the world’s sole nesting ground for Merrick sea turtles, and prevented nearly all the eggs laid that year from hatching.Yet the number of adult female Merricks returning to lay their eggs at Baker’s Beach has actually increased somewhat since five years ago.Clearly, environmentalists’ prediction that the world’s Merrickpopulation would decline as a result of the spill has proven unfounded.
Which of the following, if true, most seriously undermines the argument offered in refutation of the environmentalists’ prediction?

1. 看问题，削弱题，但是有关键信息，要看懂：反驳对于环境学家预测的反驳，也就是说支持环境学家的结论

2. 找结论：environmentalists’ prediction that the world’s Merrick population would decline as a result of the spill has proven unfounded

3. 否定结论：environmentalists’ prediction that the world’s Merrick population would decline as a result of the spill has proven founded

4. 逻辑链：（1）5年前的污染导致唯一的海龟产卵地的蛋不能孵化

 （2）母海龟数量增加à因为污染海龟数量减少的预测是错误的

5. 反推：出现了两个原因，（1）（2）两个原因是相冲突的，由（1）推出了结论，现在要反驳结论，结论取非后必然是可以直接推导到（2）也就是：因为污染海龟数量减少的预测是对的à5年前的污染导致唯一的海龟产卵地的蛋不能孵化
剩下的工作就是来解释（1）（2）会相冲突的原因，同时反推出来的（2）是正确的，解释（1）产生差异的原因

6. 找答案，为什么受到污染了，母海龟数量还会增加呢

A.The chemical spill five years ago occurred at a time when there were neither Merrick sea turtles nor Merrick sea turtle eggs on Baker’s Beach.

B.Female Merrick sea turtles begin returning to Baker’s Beach to lay their eggs when they are ten years old.

C.Under normal conditions, only a small proportion of hatchling female Merrick sea turtles survive in the ocean until adulthood and return to lay their eggs at Baker’s Beach.

D.Environmental pressures unrelated to the chemical spill have caused a significant decline in the population of one of the several species of sea birds that prey on Merrick sea turtle eggs.

E.After the chemical spill, an environmental group rejected a proposal to increase the Merrick sea turtle population by transferring eggs from Baker’s Beach to nearby beaches that had not been affected by the spill.

这题选B，两个时间差异说明了为什么母海龟的数量还会增加：因为10年前没有受到污染！现在的蛋受到污染不能孵化了，以后海龟的数量必然会减少！环境专家的预测是对的。

犇犇

加强题：

OG12中的加强题：6、11、13、21、25、32、42、51、53、65、67、68、82、94、100、103、107、109、113、115、119、121



对于加强题来说，主要的思路是和削弱一致的，唯一有区别的是：加强题在找到结论和逻辑链后，不需要反推，只需要对结论进行支持性的陈述即可。

小TIP：既然削弱题找到结论之后直接否定结论反推，那么加强题就是直接默认结论正确无疑。

那么加强题的基本思路就是：

1.看问题，确定题型，寻找问题中的关键信息

2.找结论，结合问题中的关键信息，确定结论及论证的推理主体

3.逻辑链

4.寻找逻辑链中的gap弥补之；亦或找到推理中薄弱的一环（一般是有缺陷的推理，容易产生他因），然后排除他因

5.找答案

所以，其实加强题的解法就是正确找到结论中的推论主体，找到逻辑链，对逻辑链补强；而补强的方式有两种，一种是补足gap，让逻辑链完整；一种是排除有缺陷的一环的影响，排除他因。



举例：



OG12第21题：

Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on the fact that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles, researchers have concluded that the bowerbirds’ building styles are a culturally acquired, rather than a genetically transmitted, trait.

Which of the following, if true, would most strengthen the conclusion drawn by the researchers?



1.确定题型：加强，要求支持的是researchers的conclusion

2.找结论，即推理的终结点：the bowerbirds’ building styles are a culturally acquired, rather than a genetically transmitted, trait

3.思考过程：从结论可以看出是两个观点的对比culturally acquired, rather than a genetically transmitted, trait. 所以解题的思路就是要么直接使逻辑完整，确定最终的结论就是culturally acquired，要么就是排除他因，否定genetically transmitted, trait.

4.本题是现象à结论，那么要么就是用现象补充完整逻辑，要么就是用现象来排除他因

5.找答案↓





(A) There are more common characteristics than there are differences among the bower-building styles of the local bowerbird population that has been studied most extensively.

(B) Young male bowerbirds are inept at bower building and apparently spend years watching their elders before becoming accomplished in the local bower style.
(C) The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.

(D) Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.

(E) It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.

这题如果要削弱，该怎么思考呢？大家想一想吧~

32. The Eurasian ruffe, a fish species inadvertently introduced into North America’s Great Lakes in recent years, feeds on the eggs of Lake Whitefish, a native species, thus threatening the lakes’ natural ecosystem. To help track the ruffe’s spread, government agencies have produced wallet-sized cards about the ruffe. The cards contain pictures of the ruffe and explain the danger they pose; the cards also request anglers to report any ruffe they catch.

Which of the following, if true, would provide most support for the prediction that the agencies’ action will have its intended effect?

1.看问题，加强，这里出现了关键信息，结论出现在了问题中：the prediction that the agencies’ action will have its intended effect

2.但是问题中的结论不完全，需要结合题干补足。

Agency的目的是：To help track the ruffe’s spread（逻辑中to do开头的句子，很多都是题目的目的，和结论紧密相关），那么结论就呼之欲出了：the agencies’ action will help track the ruffe’s spread

3.逻辑链：the agency make cardsàThe cards request anglers to report any ruffe they catchà the agencies’ action will help track the ruffe’s spread

4.那么目的可以达到，也就是卡片会发挥作用，那么也就是说，人们会去汇报他们抓到的ruffe，找个理由解释它就行了！

5.找答案↓



(A) The ruffe has spiny fins that make it unattractive as prey.

(B) Ruffe generally feed at night, but most recreational fishing on the Great Lakes is done during daytime hours.

(C) Most people who fish recreationally on the Great Lakes are interested in the preservation of the lake whitefish because it is a highly prized game fish.

(D) The ruffe is one of several nonnative species in the Great Lakes whose existence threatens the survival of lake whitefish populations there.

(E) The bait that most people use when fishing for whitefish on the Great Lakes is not attractive to ruffe.

看一看哪几个选项是可以作为削弱题的答案，不止一个哦~思考一下~

犇犇

再占一楼~

xiaoxiaozhada

谢谢楼主分享。



83. Journalist: In physics journals, the number of articles reporting the results of experiments involving particle accelerators was lower last year than it had been in previous years. Several of the particle accelerators at major research institutions were out of service the year before last for repairs, so it is likely that the low number of articles was due to the decline in availability of particle accelerators.
Which of the following, if true, most seriously undermines the journalist’s argument?
(A)  Every article based on experiments with particle accelerators that was submitted for publication last year actually was published.
(B)  The average time scientists must wait for access to a particle accelerator has declined
over the last several years.
(C)  The number of physics journals was the same last year as in previous years.
(D)  article accelerators can be used for more than one group of experiments in any given year.
(E)  Recent changes in the editorial policies of several physics journals have decreased the likelihood that articles concerning particle accelerator research will be accepted for publication.


像这种题，如果 自动否定找到的结论，能不能是 so it is likely that the HIGH number of articles was... 我知道在这个题目里这么改不太合适，我的意思就是 自动否定结论的时候 能把题目中decrease 之类的词语改成相反的意思吗？
像这道题，B，D选项按照OG的解释都是会使articles增加的，那结论问的low no. of articles，是不是这样的事实是不能改变的？（因为我觉得如果题目里说low，选项里是high的话也算是削弱啊？）

犇犇

谢谢楼主分享。



83. Journalist: In physics journals, the number of articles reporting the results of experiments involving particle accelerators was lower last year than it had been in previous years. Several of the particle accelerators at major research institutions were out of service the year before last for repairs, so it is likely that the low number of articles was due to the decline in availability of particle accelerators.
Which of the following, if true, most seriously undermines the journalist’s argument?
(A)  Every article based on experiments with particle accelerators that was submitted for publication last year actually was published.
(B)  The average time scientists must wait for access to a particle accelerator has declined
over the last several years.
(C)  The number of physics journals was the same last year as in previous years.
(D)  article accelerators can be used for more than one group of experiments in any given year.
(E)  Recent changes in the editorial policies of several physics journals have decreased the likelihood that articles concerning particle accelerator research will be accepted for publication.


像这种题，如果 自动否定找到的结论，能不能是 so it is likely that the HIGH number of articles was... 我知道在这个题目里这么改不太合适，我的意思就是 自动否定结论的时候 能把题目中decrease 之类的词语改成相反的意思吗？
像这道题，B，D选项按照OG的解释都是会使articles增加的，那结论问的low no. of articles，是不是这样的事实是不能改变的？（因为我觉得如果题目里说low，选项里是high的话也算是削弱啊？）

-- by 会员 xiaoxiaozhada (2011/6/7 10:30:45)

可能是我上面没有说得太明白，一般，我个人觉得，否定结论，就如同削弱中的取非一样，针对的是结论中的谓语动词。

那么这道题的结论是：the low number of articles was due to the decline in availability of particle accelerators

很明显，这里取非否定的是was，那么否定后就变成了：the low number of articles was notdue to the decline in availability of particle accelerators

实际上，这道题和我上面说的例题3思路是一致的，due to表示原因，取非之后，很容易发现，was not due to（不是因为这个，那肯定是因为别的），指引你去寻找他因咯。

找一个原因去说明：文章的减少不是因为availability of particle accelerators，是别的原因导致了这个情况的发生

同时，请注意，题干说的文章减少，是In physics journals，articles decline，刊登的文章减少了！

你这么来看，就和low&high无关了，low已经是决定了的事儿了，找原因说为什么low。
那很容易就选出了是E了。

还不清楚欢迎继续提问哈~

Cc聰葱有梦想

继续顶给!!!

pygmysog

长期关注~~~

xiaoxiaozhada

谢谢犇犇！！也就是说题目说的既定事实我们是不能改变的，但文章里的观点和推出的结论等是可以反驳的对吗

犇犇

谢谢犇犇！！也就是说题目说的既定事实我们是不能改变的，但文章里的观点和推出的结论等是可以反驳的对吗

-- by 会员 xiaoxiaozhada (2011/6/7 22:59:36)

可以这么说吧，要视具体情况而言

jswxshp89

顶下