GMAT逻辑疑难杂症之一：复合混合型结构

　　GMAT逻辑疑难杂症之一：复合混合型结构,GMAT CR部分考察的演绎推理涉及主要以因果关系（cause-effect），前提结论（premise-conclusion）和手段目（plan-goal）的三种结构为主，针对三种结构的解题方法和技巧相信很多同学有所了解或掌握，但是随着GMAT逻辑题目的篇幅越来越长的趋势，另外一种综合了因果关系和前提结论或者手段目的和两种结构的题目在现在的考试中出现的越来越频繁，让很多学习该模块的同学在解题过程中感到无从下手抑或即使选对答案也找不到对该类型结构的相对清晰的思路。那么今天我们就围绕这种复杂的结构来说一下该种结构的解题思路。

　　首先我们先说几种混合结构的具体形式。第一种结构用“~”表示，第二种结构用“-”表示。

　　1.Premise:cause-effect~conclusion

　　该结构的第一层第一种是Premise~conclusion，第二层第二种结构是cause-effect。对于复合结构来说，三种常规结构的演绎题目的相关手段依然适用。以上面这种结构为例，如果题目是削弱题，我们同样可以按照削弱它的第一种前提结构的思路找答案，当然答案也可能是削弱第二种结构的因果关系的信息。请看例题

　　例题.Because no employee wants to be associated with bad news in the eyes of a superior, information about serious problems at lower levels is progressively softened and distorted as it goes up each step in the management hierarchy. The chief executive is, therefore, less well informed about problems at lower levels than are his or her subordinates at those levels.

　　The conclusion drawn above is based on the assumption that

　　(A) Problems should be solved at the level in the management hierarchy at which they occur.

　　(B) Employees should be rewarded for accurately reporting problems to their superiors.

　　(C) problem-solving ability is more important at higher levels than it is at lower levels of the management hierarchy.

　　(D) Chief executives obtain information about problems at lower levels from no source other than their subordinates.

　　(E) Some employees are more concerned about truth than about the way they are perceived by their superiors.

　　解题思路：文章整体的结构是前提结论结构，其中最后一句中的therefore也是典型的表结论常用的信号词。那么前面一句是该结论的前提。我们再分析结构的过程发现，很多同学会把一开始的基逗号前面because开头的信息当作是前提，如果这样认定那么解题就会出现大麻烦，因为该信息是题目前提部分的原因，准确地说题目的前提就是该部分的后半句即“information about serious problems at lower levels is progressively softened and distorted as it goes up each step in the management hierarchy”，如果再精简则是“information about serious problems at lower levels is progressively softened and distorted”当最关键的结构和关键信息分析清楚之后，解题就变的非常容易了。接下来我们应用好两种结构常规的假设题方法找答案即可。

　　正确答案是D,取非之后攻击了结论。

　　例题

In the past, teachers, bank tellers, and secretaries were predominantly men; these occupations slipped in pay and status when they became largely occupied by women. Therefore, if women become the majority In currently male-dominated professions like accounting, law, and medicine, the income and prestige of these professions will also drop.

　　Which of the following, if true, would most likely be part of the evidence used to refute the conclusion above?

　　A. Accountants, lawyers, and physicians attained their current relatively high levels of Income and prestige at about the same time that the pay and status of teachers, bank tellers, and secretaries slipped.

　　B. When large numbers of men join a female-dominated occupation, such as airline flight attendant, the status and pay of the occupation tend not to change.

　　C. The demand for teachers and secretaries has increased significantly in recent years, while the demand for bank tellers has remained relatively stable.

　　D. If present trends in the awarding of law degrees to women continue, it will be at least two decades before the majority of lawyers are women.

E. The pay and status of female accountants, lawyers, and physicians today are governed by significantly different economic and sociological forces than were the pay and status of female teachers, bank tellers, and secretaries in the past.

　　解题思路：该结构和上面一道题目的结构一样，同样是整体结构为前提结论，而前提是因果关系。答案是E选项。该选型攻击了前提即以第一句话中的因果关系。该因果关系是通过时间上的否定：现在否定过去或者将来否定现在的中的前者-即：现在否定过去。说明过去的原因和现在的原因不一样，同样也意味着过去的结果在现在就不会再出现了。我们现在回到题目整体结构上来，前提被否定了，那么相应的结论也不成立。

　　2. 多层次多类别结构

　　goal1，goal2-

　　多层次多类别结构，该种结构是把演绎题目的结构和信息多层次化结合的一种登峰造极的题型，以至于很多同学对于该类题目无从下手。复杂的东西我们更需要抽丝剥茧，捋清楚结构和层次后，应用已掌握的方法和技能解题。请看题

To reduce waste of raw materials, the government of Sperland is considering requiring household appliances to be broken down for salvage when discarded. To cover the cost of salvage, the government is planning to charge a fee, which would be imposed when the appliance is first sold. Imposing the fee at the time of salvage would reduce waste more effectively, however, because consumers tend to keep old appliances longer if they are faced with a fee for discarding them.

　　该题型的结构和层次如下：

　　解题思路：如上图所示，如果题目是削弱题或者假设或加强题，我们可以从表格中任何一个信息按照该结构所对应的方法进行削弱或加强或者寻找信息。在这里同学们可能会感觉即使方向明确了，但是对于这么复杂的信息依然会感到复杂而找不到着手点。这里补充一个解决逻辑题目的重要原则就是：题目的重点信息在后半段尤其是最后一句是重中之重。回到题目，我们会发现题目的最后一句话是由however引导的一个表因果关系的，同时又是作为该结构目的的一种手段，所以该信息的各种特征表明了，文中的考察重点大概率会是这个信息。

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

　　(A) Increasing the cost of disposing of an appliance properly increases the incentive to dispose of it improperly.

　　(B) The fee provides manufacturers with no incentive to produce appliances that are more durable.

　　(C) For people who have bought new appliances recently, the salvage fee would not need to be paid for a number of years.

　　(D) People who sell their used, working appliances to others would not need to pay the salvage fee.

　　(E) Many nonfunctioning appliances that are currently discarded could be repaired at relatively little expense.

　　当我们看完所有题目发现，唯有A选项的内容是和题目的核心信息有关系的，进一步分析我们发现A选项的内容正如我们上面分析的是攻击最后一个手段中的因果关系中的结果--用其他原因攻击了结果。

　　小结：因为国内师生共同努力的结果，再加上国内针对每门考试的应试水平，使得我们对于每一门考试包括GMAT考试的应试水平达到了一定的高度。GMAC也意识到了这种情况，一方面制定相应的措施管制鸡精等内容，暗着也在题目的考法和难度上不断地加码。大家要记住一点的是，尽管随着时间GMAT题目的难度系数相对过去的题目有所增加，正如对解决上述题目所需要的知识和解题思路一样，不管官方再怎么加码，也不会超出该考试每个部分考察的核心内容和能力的范畴。所以应对变化最好的方法踏踏实实把该学的内容学会了，该练的练到了，该提高的能力提高了，才能做到以不变应万变，出分就是水到渠成的事情。