今天小编就从推理模式的角度为大家简单的讲解逻辑题中的那几种推理模式，以及我们如何判别这些推理模式，和如何运用这种知识解题。
一、GMAT逻辑推理模式的理解
1、GMAT逻辑推理模式的定义。
GMAT逻辑其实考的是评估论证，简单来说就是论证前提和结论之间的关系。而在你评估论证之前，是要首先知道这个论证的构建方式。在非形式逻辑学领域这种种评估论证的方法叫做Critical Question，简称CQ。不同的逻辑推理模式下CQ的方向和数量完全不同，通过了解不同的推理模式，就掌握了正确答案的方向。
2、GMAT逻辑中类比推理模式的定义。
类比推理模式大致的定义是：两个事情(A,B)的相同点列出来，然后再给出A的一个特点，推理B也应该具有这个特点，B的这个特点就是原文的结论。
题目形式如： A和B都有特点 D1，D2，……Dn，可由A有X, 推出B有X。
抽象形式：Premises：A和B有相似点，A有某个特点。Conclusion：B也有这个特点。
(详情请看 GMAT逻辑常见推理模式解析 )
二、GMAT逻辑类比推理解题技巧
1、类比推理的评估方向(正确答案的倾向)。
CQ1：相似性问题。A,B这两个案例真的相似吗?若都一样，那么加强推理;若有一个可能的不相似点，那么削弱推理。这种说不相似点的选项最容易被错误的排除掉，容易被当做无关。
CQ2：反案例问题。是否存在一个反案例C?若不存在反案例，则加强推理;若存在一个C，使其具有AB的相似点，但是不具有结论中要推断的相似点，则削弱推理。
2、类比推理的解题技巧。
正确选项中一定涉及了两个案例，或出现和题目中两个案例完全不一样的案例。如果选项只涉及题目中出现的一个案例那么排除。
3、类比推理解题的注意事项。
A在GMAT题目中一定不会出现两个选项分别属于两个CQ的方向。因为CQ1和CQ2是同等强度的，无法区分。有大概5%的题目会出现两个选项同属于一个CQ，直接比较强弱。大部分情况下是为了严谨表达，而绝非让你直接比较选项。
B类比的核心是就相似点比相似点。不是说题目中凡事出现两个东西的题就是类比题。
(详情请看 GMAT逻辑的推理模式 )
三、GMAT逻辑链充分必要条件举例分析
When there is less rainfall than normal, the water level of Australian rivers falls and the rivers flow more slowly. Because algae whose habitat is river water grow best in slow-moving water, the amount of algae per unit of water generally increases when there has been little rain. By contrast, however, following a period of extreme drought, algae levels are low even in very slow-moving river water.
Which of the following, if true, does most to explain the contrast described above?
(A) During periods of extreme drought, the populations of some of the species that feed on algae tend to fall.
(B) The more slowly water moves, the more conducive its temperature is to the growth of algae.
(C) When algae populations reach very high levels, conditions within the river can become toxic for some of the other species that normally live there.
(D) Australian rivers dry up completely for short intervals in periods of extreme drought.
(E) Except during periods of extreme drought, algae levels tend to be higher in rivers in which the flow has been controlled by damming than in rivers that flow freely.
类比推理，因此要找到两者的不同点或者举出个例子有相同点但结果完全相反：
|
When there is less rainfall than normal |
a period of extreme drought |
B 水的确流的慢，如果气温也适宜应该长得好啊。 A 没有天敌来干扰应该长得好才对。
C 对别的生物来说有毒不影响A 自己的数量。
D 正确。在极度干旱下水都没了(找到一个不同点)，那么就长不了了。
E 题目比较的不是干旱条件下不同的水流。
92. In the country of Veltria, the past two years’ broad economic recession has included a business downturn in the clothing trade, where sales are down by about 7 percent as compared to two years ago. Clothing wholesalers have found, however, that the proportion of credit extended to retailers that was paid off on time fell sharply in the first year of the recession but returned to its prerecession level in the second year.
Which of the following, if true, most helps to explain the change between the first and the second year of the recession in the proportion of credit not paid off on time?
(A) The total amount of credit extended to retailers by clothing wholesalers increased between the first year of the recession and the second year.
(B) Between the first and second years of the recession, clothing retailers in Veltria saw many of their costs, rent and utilities in particular, increase.
(C) Of the considerable number of clothing retailers in Veltria who were having financial difficulties before the start of the recession, virtually all were forced to go out of business during its first year.
(D) Clothing retailers in Veltria attempted to stimulate sales in the second year of the recession by discounting merchandise.
(E) Relatively recession-proof segments of the clothing trade, such as work clothes, did not suffer any decrease in sales during the first year of the recession.
找两年的不同点：
|
Recession第一年 |
Recession第二年 |
B 如果cost提高那还款压力应该更大，所以应该提高才对。 A 如果第二年给的credit多了应该相应的延期付款率提高。
C 正确。很多第一年承受不住压力要退出行业，就会延期付款，而第二年retailers少了，因此延期付款率降低。
D 打折不一定提升了收益。
E 如果第一第二年一样的话那没什么好比了，延期付款率就不会变化。
(详情请看 GMAT逻辑练习题)
以上是小编举例为大家分析了两个类比模式解题分例子，当然事件A和事件B之间的异同点还是要大家自己从题干当中提炼，然后分析。百利天下小编相信大家都能够得到答案。
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