我对逻辑题的感受

蓝夕叶子

斑斑大作，顶～

ethyl

继续：

六、 Weaken题

削弱题在OG里面达到80道左右，可见其重要性；为什么ETS这么偏爱这种题型呢？我觉得这跟GMAT考试的宗旨是有一定联系的。进入商学院学习的学生需要有一定的辩驳思维，不能人云亦云、亦步亦趋，而又有自己的想法，遇到一个问题、一个观点都要惯性得进行思辨；这样在以后的生活中才能养成独立思考、解决问题的习惯。

知道问题是削弱题后开始读文章，大牛们经常说每读一句话都要思考在文章中的作用（比如mindfree总结的active reading），可是我却往往做不到，我能做的就是在读完题后努力找出结论，那么除了结论剩下的应该就是为结论服务的东东了（听着像废话，俺就是这么做的）。

然后就是挑选项了。没什么好说的，记住精准的结论找答案。

其实，我觉得削弱题和支持题的检验是相对而言比较难的，不像假设题可以代入题中看是不是必要条件；检验削弱题的时候，lawyer大虾这么说：问自己，是否该答案使作者再考虑他的观点或迫使作者做出反应或原文该前提能证明该结论吗。这个就比较难以把握，选项是自己选出来的，当然首先就认为它是削弱的，问自己有时候问不出来什么东西。我觉得这个时候，可以稍微花几秒钟时间，回到题中，重新把结论看一遍，看看自己第一遍看的时候有没有什么遗漏的或者不对的地方，然后再核实你认为正确的选项；当然，如果你很确认结论没记错，那么，就大胆选吧。

需要注意的细节：

1)         有几种比较特殊的类型。一种是结论为因果关系的：削弱方式大概包括他因、断裂（同因异果或者异因同果）、因果颠倒等。请看下面例题：

断裂：OG-9的D选项

OG-9.

A conservation group in the United States is trying to change the long-standing image of bats as frightening creatures. The group contends that bats are feared and persecuted solely because they are shy animals that are active only at night.

Which of the following, if true, would cast the most serious doubt on the accuracy of the group’s contention?

D. Raccoons and owls are shy and active only at night; yet they are not generally feared and persecuted.（D）

OG对D的解释：

The group’s contention suggests that animals that are shy and active at night are feared and persecute for that reason. D establishes that raccoons and owls are shy and active at night, but that they are neither feared nor persecuted. Therefore, D is the best answer.

因果颠倒：OG-137的

OG-137.

A study of marital relationships in which one partner's sleeping and waking cycles differ from those of the other partner reveals that such couples share fewer activities with each other and have more violent arguments than do couples in a relationship in which both partners follow the same sleeping and waking patterns. Thus, mismatched sleeping and waking cycles can seriously jeopardize a marriage.

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

(D) People in unhappy marriages have been found to express hostility by adopting a different sleeping and waking cycle from that of their spouses.（D）

OG对D的解释：

The argument assumes that mismatched sleeping and waking cycles precede martial problems. Choice D weakens the argument by indicating that this assumption is false, and D is the best answer.

2)         结论为条件结论的。削弱方式就是当前提成立的时候，结论不成立；即充分条件被满足的时候，必要条件不能成立。尤其需要注意的是，对前提（即充分条件）的削弱是无效的。请看下面例题：

OG-2.

The average life expectancy for the United States population as a whole is 73.9 years, but children born in Hawaii will live an average of 77 years, and those born in Louisiana, 71.7 years. If a newlywed couple from Louisiana were to begin their family in Hawaii, therefore, their children would be expected to live longer than would be the case if the family remained in Louisiana.

Which of the following, if true, would most seriously weaken the conclusion drawn in the passage?

C. The longevity ascribed to Hawaii’s current population is attributable mostly to genetically determined factors.（C）

OG对C的解释：

C is the best answer. This choice suggests that a significant proportion of Hawaii’s population is genetically predisposed to be long lived. Since Louisianans are not necessarily so predisposed, and since the Louisianans’ children will acquire their genetic characteristics from their parents, not from their birthplace, this choice presents a reason to doubt that Hawaiian born children of native Louisianans will have an increased life expectancy. Therefore, this choice is the best answer.

简单一点说就是，L夫妇如果在H生了孩子，那么也不一定活那么久；因为基因不同。

3)         错误选项包括无关选项、加强选项等。

OG-41.

Since the mayor’s publicity campaign for Greenville’s bus service began six months ago, morning automobile traffic into the midtown area of the city has decreased seven percent. During the same period, there has been an equivalent rise in the number of persons riding buses into the midtown area. Obviously, the mayor’s publicity campaign has convinced many people to leave their cars at home and ride the bus to work.

Which of the following, if true, casts the most serious doubt on the conclusion drawn above?

A. Fares for all bus routes in Greenville have risen an average of five percent during the past six months.

B. The mayor of Greenville rides the bus to City Hall in the city’s midtown area.

C. Road reconstruction has greatly reduced the number of lanes available to commuters in major streets leading to the midtown area during the past six months.

D. The number of buses entering the midtown area of Greenville during the morning hours is exactly the same now as it was one year ago.（C）

E. Surveys show that longtime bus riders are no more satisfied with the Greenville bus service than they were before the mayor’s publicity campaign began.

OG对ADE（支持）及B（无关）的解释：

A eliminates decreased fares as a possible explanation for the increased ridership, so it supports rather than casts doubt on the conclusion.

D eliminates a possible explanation-that the increased ridership is a result of extra buses-and thus supports the conclusion rather than casts doubt on it.

E eliminates a possible explanation-that the increased ridership is a result of improved service-and thus supports the conclusion rather than casts doubt on it.

B. The mayor of Greenville rides the bus to City Hall in the city’s midtown area.

[此贴子已经被作者于2005-8-5 22:13:21编辑过]

ethyl

七、 Must Be True

这类题可能就是新东方FeiFei讲义上所说的归纳题吧。

标志词：conclusion、inferred、implied、supported、if above true, then it is also true等

关于support，如果提问形式如the statement above support which of the following，则表示归纳（must be true），如果提问形式如which of the following, if true, best support the conclusion, 则表示加强。

读题的时候FeiFei讲义上说：不要关心文章的推导过程，尽量减少思维，承认文章正确，只抓信息。对于此，我不敢苟同，因为实战中，用这种方法就可以搞定的题好像不是很多，至少我是这样认为的；如果四五行的单词读下来，不思考是怎样逻辑得联系在一起的，对做题的信心就是很大的打击。我更赞同lawyer的方法，简单点说就是：有结合点的就结合起来，有推理链的就将推理链提出来，什么都没有那就只好记住文章的内容。

看选项的时候最重要的还是排除法，因为归纳题要求答案的必须是文中的内容或者文中的内容能够推出来的；当然，有的题目很明显，比如结合点很多，结合的很紧密，或者充分必要性很强，这种情况下，正确答案是可以事先猜出来的。

需要注意的细节：

1)         错误选项包括无关选项、推理错误选项（OG-169的D）等。

OG-169.

Corporate officers and directors commonly buy and sell, for their own portfolios, stock in their own corporations. Generally, when the ratio of such inside sales to inside purchases falls below 2 to 1 for a given stock, a rise in stock prices is imminent. In recent days, while the price of MEGA Corporation stock has been falling, the corporation’s officers and directors have bought up to nine times as much of it as they have sold.

The facts above best support which of the following predictions?

(A) The imbalance between inside purchases and inside sales of MEGA stock will grow even further.

(B) Inside purchases of MEGA stock are about to cease abruptly.

(C) The price of MEGA stock will soon begin to go up.

(D) The price of MEGA stock will continue to drop, but less rapidly.（C）

(E) The majority of MEGA stock will soon be owned by MEGA’s own officers and directors.

OG对无关选项（ABE）及错误推理选项的解释：

Since the prediction in choice D runs counter to the stated generalization, choice D is not supported.

The passage does not suggest there will be an increase in the imbalance between such purchases and sales. Thus, choice A is not supported.

Similarly, the passage suggests neither that inside purchases are about to cease nor that the majority of MEGA stocks will soon be owned by MEGA officers and directors. Thus, neither choice B nor choice E is supported.

2)         推理错误选项可能是原文某命题的逆命题或者否命题或者将充分条件或必要条件加not（OG-25的B）等。

OG-25.

If there is an oil-supply disruption resulting in higher international oil prices, domestic oil prices in open-market countries such as the United States will rise as well, whether such countries import all or none of their oil.

Which of the following conclusions is best supported by the statement in the passage?

B. International oil-supply disruptions have little, if any, effect on the price of domestic oil as long as an open-market country has domestic supplies capable of meeting domestic demand.

C. The oil market in an open-market country is actually part of the international oil market, even if most of that country’s domestic oil is usually sold to consumers within its borders.（C）

OG对B的解释：

B and D are not supported, since each contradicts the claim that an international oil-supply disruption will lead to rising oil prices in an open-market nation.

3)         不能用数字推比例，反之亦然（OG-117的A）

OG-117. A company’s two divisions performed with remarkable consistency over the past three years: in each of those years, the pharmaceuticals division has accounted for roughly 20 percent of dollar sales and 40 percent of profits, and the chemicals division for the balance.

Which of the following can properly be inferred regarding the past three years from the statement above?

(A) Total dollar sales for each of the company’s divisions have remained roughly constant.

(C) The chemicals division has realized lower profits per dollar of sales than has the pharmaceuticals division.（C）

OG对A的解释：

The passage provides no information about total dollar sales, so choice A is incorrect,

4)         答案可能是原文某句话的重写或逆否命题或某几句话的重写（OG-11）

OG-11.

The fewer restrictions there are on the advertising of legal services, the more lawyers there are who advertise their services, and the lawyers who advertise a specific service usually charge less for that service than lawyers who do not advertise. Therefore, if the state removes any of its current restrictions, such as the one against advertisements that do not specify fee arrangements, overall consumer legal costs will be lower than if the state retains its current restrictions.

If the statements in the passage are true, which of the following must be true?

C. If the restriction against advertisements that do not specify fee arrangements is removed, more lawyers will advertise their services.（C）

OG对C的解释：

The supposition in c involves reducing by one the number of restrictions on the advertising of legal services. Any such reduction will, if the stated correlation exists, be accompanied by an increase in the number of lawyers advertising their services, as C predicts. Therefore, C is the best answer.

还要再说一点，经常发现有这样的选项，文中说某事物A（的价格、数量等）增长或者减少了，而某选项说组成A的各个部分（的价格、数量等）是怎么增长或者减少的；其实这样的选项一般情况下是无关的。如下面例题：

OG-15.

The cost of producing radios in Country Q is ten percent less than the cost of producing radios in Country Y. even after transportation fees and tariff charges are added, it is still cheaper for a company to import radios from Country Q to Country Y than to produce radios in Country Y.

The statements above, if true, best support which of the following assertions?

A. labor costs in Country Q are ten percent below those in Country Y.

C. the tariff on a radio imported from Country Q to Country Y is less than ten percent of the cost of

manufacturing the radio in Country Y.（C）

E. it takes ten percent less time to manufacture a radios in Country Q than it does in Country Y.

OG对AE的解释：

A and E give possible partial explanations for the cost difference, but neither is supported by the passage because the cost advantage in Q might be attributable to other factors.

之所以将最后一点单独列出，是因为这一点不仅在归纳题里面出现，而且在其他类型的题目里面也经常出现。

欢迎大家批评斧正！

[此贴子已经被作者于2005-8-7 22:23:13编辑过]

ethyl

八、 填空

填空题在OG里占到了7道，而且都比较简单，一般是不需要推导的，只需要记住文章说了什么东西然后找选项就可以。

另外呢，需要补出的部分所在的那句话很重要，有的问下面哪个是例子或者表现，有的问现象的原因等等，知道了这句话在讲什么，找选项的时候才能有的放矢。

看选项的时候排除无关选项仍然是非常重要的方法，因为正确的选项本身就是文章的一步分；但是，在举例题中，无关排除好像就无用武之地了。如下例题：

OG-38.

Which of the following best completes the passage below?

Established companies concentrate on defending what they already have. Consequently, they tend not to be innovative themselves and tend to underestimate the effects of the innovations of others. The clearest example of this defensive strategy is the fact that___.

A. ballpoint pens and soft-tip markers have eliminated the traditional market for fountain pens, clearing the way for the marketing of fountain pens as luxury or prestige items

B. a highly successful automobile was introduced by the same company that had earlier introduced a model that had been a dismal failure

C. a once-successful manufacturer of slide rules reacted to the introduction of electronic calculators by trying to make better slide rules

D. one of the first models of modern accounting machines, designed for use in the banking industry, was purchased by a public library as well as by banks（C）

E. the inventor of a commonly used anesthetic did not intend the product to be used by dentists, who currently account for almost the entire market for that drug.

问：最能体现防御策略的例子？

其实防御策略有两部分组成：不思创新；鄙视别人的创新。要同时满足这两个条件才能选。

A选项好像提到了创新（旧产品市场定位改变），但是没有体现对别人的创新的反应。错

B两点都没有体现。

C没有尝试新的产品，所以不思创新；对于新产品，采取将老产品优化的办法，所以是鄙视别人的创新。

DE两者都没有体现。

由本题我们可以看出来，即使在填空题里，大家做题的时候也需要尽量记住多并且准的原文信息。

九、 Boldface

这类题又叫句子作用题，OG中只有一道，却非常经典。

其实，如果一个论证过程只有一个论据和一个论点，那么很简单，不用出五个选项让大家选各个部分之间的关系；所以呢，出题机构会把论证过程写得详细一点，比如最常见的，首先说出一个观点，并且可能给出一两个论据来支持，然后说存在另一种情况或者观点，理所当然第二个结论及论据也出现了。不能再复杂了，否则大家都会受不了，选项也会庞大无比。

知道了这点就很简单了，有时候甚至不用读懂文章或者读完文章就可以知道ETS要干什么，因为文中通常会有转折词，如however, but等等，那么这个转折词可以将文章分成两部分，很有可能就是前面一种情况，后面一种情况。这样看boldface的关系就简单多了。

欢迎大家斧正！

[此贴子已经被作者于2005-8-8 20:20:59编辑过]

ethyl

备用！

iwillfly

谢谢牛牛们的无私奉献！UP

boyray

对NN的景仰。。。简直不知道该说什么了。。。

zx_nju

看完了.确实是个好贴.希望还有多多

beechanooi

好文，好文！敬佩，敬佩！请教NN，我怎么样才能把此文收藏起来啊？

esprit

楼上的：

用复制粘贴放到word里保存起来哈。