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GMAT逻辑解题关键

发布时间:2008-8-1 文字大小:  打印:打印此文

要到美国商学院读研究生的同学往往需要考GMAT。

GMAT没有GRE中的类比反义和填空,免去了背大量生僻单词的负担,但增加了逻辑(critical reasoning)和语法改错(sentence correction)

其实过去的GRE也是有单项的逻辑题,但后来去除了,然后做为一种题型出现在了阅读之中。

逻辑题是很有意思的,每做一道题,就像玩一个game。我将之誉为“大脑的体操,思维的游戏,精神的调节,智商的飘逸。”

但真正面对考试,就不那么轻松,因为有时间所限。尤其是难题,运用严格的逻辑思维来做,往往耗时甚多。尤其是五个选项逐一论证更是不切实际。所以对于逻辑题,我们必须要培养一种感觉,依靠这种感觉我们可以很快地将一些无关项排除掉。那这种感觉除了靠大量练习来培养外,更应通过察觉选项中的“无关信息”,迅速做出判断,将之排除。

这就是所谓“无关信息排除法”--- 通过选项中出现了与原文内容和推理无关的内容将之迅速排除。常常能排除五项中的三个,再对剩下的选项认真考虑,做出最后抉择。

具体实践两道题

Teenagers are often priced out of the labor market by the government-mandated minimum-wage level because employers cannot afford to pay that much for extra help. Therefore, if Congress institutes a subminimum wage, a new lower legal wage for teenagers, the teenage unemployment rate, which has been rising since 1960, will no longer increase.

(注释:priced out of the market:因价高而被挤出市场)

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

(A) Since 1960 the teenage unemployment rate has risen when the minimum wage has risen.

(B) Since 1960 the teenage unemployment rate has risen even when the minimum wage remained constant.

(C) Employers often hire extra help during holiday and warm weather seasons.

(D) The teenage unemployment rate rose more quickly in the 1970’s than it did in the 1960’s.

(E) The teenage unemployment rate has occasionally declined in the years since 1960.

先看完问题,发现是削弱题;再读原文,意思不难,很快提炼出其逻辑为

如果国会制定更低的teenagers最低工资 ===》teenagers的失业率将不再上升

显然,正确选项首先要涉及最低工资和失业率之间的关系,而其他内容则为无关信息,可以排除

显然A 和B都是相关的

而C在谈季节问题,D和E没有涉及失业率快慢的原因,都与原文逻辑无关,通通排除。

所以只需要仔细审视A和B

A: “最低工资上升的时候,失业率上升”,这与原文逻辑(更低工资将导致失业率不上升)形成了“反因反果”的关系,所以是加强。(比如:“不长跑的人不长寿”加强了“长跑的人长寿”)

这样A就被排除了

所以答案只能是B

B的正面论证:

B: “最低工资不变的时候,失业率上升”说明失业率上升可能另有他因。这个论证的说服力不是很强,所以该题用排除法更有效。注意:削弱只是降低推理成立的可能性,而不需要推翻原文逻辑

“Fast cycle time” is a strategy of designing a manufacturing organization to eliminate bottlenecks and delays in production. Not only does it speed up production, but it also assures quality. The reason is that the bottlenecks and delays cannot be eliminated unless all work is done right the first time.

The claim about quality made above rests on a questionable presupposition that

(A) any flaw in work on a product would cause a bottleneck or delay and so would be prevented from occurring on a “fast cycle” production line

(B) the strategy of “fast cycle time” would require fundamental rethinking of product design

(C) the primary goal of the organization is to produce a product of unexcelled quality, rather than to generate profits for stockholders

(D) “fast cycle time” could be achieved by shaving time off each of the component processes in production cycle

(E) “fast cycle time” is a concept in business strategy that has not yet been put into practice in a factory

本着“先读问题,再看原文”的原则,首先发现是假设题(标志很明显:rest on a questionable presupposition; 不必理会questionable这个词)。然后又发现原文很绕,其中好像有两套逻辑,比较麻烦;那就看选项吧,毕竟考场上时间有限。

我们先用无关项排除法分别审视这五个选项:

(A) 所涉及的概念,无论bottleneck还是delay都出自于原文,所以先行保留

(B) 当看到最后的“product design”后,对它不抱希望了,原文实在没有产品设计方面的任何信息

(C) 看到最后的“profits for stockholders”,禁不住笑了,这不瞎扯吗?与原文无关啊。

(D) 其中的component 与原文无关了,就可以排除;再者该项的主旨是节省时间,这又犯了答非所问的错误(问题关心的是“quality”,而与时间无关)

(E) 其中的“put into practice又是瞎操心,立即排除。

考虑到B,C,D,E都不可能对,这样就确定A为答案了;一道很困难的题就这样被无关信息排除法轻松解决了

当然这道题还一种更便捷的做法 ---- 难题猜A,这个技巧使用起来很潇洒,但正确率只有less than 50%

为了更好滴理解无关信息排除法的强大,我们来看看正面论证A正确是多么的不易

分析原文:

1)先看后半部分 — 原因部分(The reason is that the bottlenecks and delays cannot be eliminated unless all work is done right the first time.)

属于Not A, unless B的推理模式,中文意为“除非有B, 否则就没有A”

举个例子: 若A = 生命,B = 空气,那意思就为“除非有空气,否则就没有生命”。显然B是A的必要条件(必要者,没它就不行啊)。我们又知道B 是A 的必要条件,就意味着A是B的充分条件(如果有生命,那就足以说明一定有空气)。重温完这一套挺耗神的充分、必要条件的关系,我们来对付这一句话:

先直译为:

“bottleneck 和delays不能被消除,除非所有工作第一次正确地做完”

那就是说:任何工作没有第一次正确做完 ===》产生bottleneck和delays

这就对应了A项的前半部分(any flaw in work on a product would cause a bottleneck or delay)

2)再看前半部分 — 结论部分(“Fast cycle time” is a strategy of designing a manufacturing organization to eliminate bottlenecks and delays in production. Not only does it speed up production, but it also assures quality.)

其意为: 用来消除bottleneck和delays的Fast cycle time能加速生产和保证质量,其中隐含了这样的假设“通过消除bottleneck和delays, Fast cycle time能够阻止产生任何差错”,这恰恰对应了A项的后半部分(any flaw in work 。。。would be prevented from occurring on a “fast cycle” production line)

综合1)和2)的成果,得出原文的假设为A

这就是对A的正面论证,实在太复杂了,在有限时间内不具有实用性。

来源:新浪教育

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