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标题: LSAT-2-2-13 [打印本页]

作者: crusaders 时间: 2004-1-5 15:42
标题: LSAT-2-2-13
13.If retail stores experience a decrease in revenues during this holiday season, then either attitudes toward extravagant gift-giving have changed or prices have risen beyond the level most people can afford. If attitudes have changed, then we all have something to celebrate this season. If prices have risen beyond the level most people can afford, then it must be that salaries have not kept pace with rising prices during the past year.
Assume the premises above to be true. If salaries have kept pace with rising prices during the past year, which one of the following must be true?
(A) Attitudes toward extravagant gift-giving have changed.
(B) Retail stores will not experience a decrease in retail sales during this holiday season.
(C) Prices in retail stores have not risen beyond the level that most people can afford during this holiday season.
(D) Attitudes toward extravagant gift-giving have not changed, and stores will not experience a decrease in revenues during this holiday season.
(E) Either attitudes toward extravagant gift-giving have changed or prices have risen beyond the level that most people can afford during this holiday season.
很好玩的一道题,给了三个条件
但答案很简单,最后一个条件逆否就直接推导出来了..
大家看看是不是我做错了

作者: 番茄炒蛋 时间: 2004-1-5 17:21
答案是对的啊，不过d很容易错，里面就是有一个很小的充分必要关系弄错了

作者: snowjing 时间: 2005-9-17 04:52

若进一步推理, 是否可以得到B.

原文推理: 总推理stores decrease-->“attitudes changed” + “prices risen”;

分推理1)attitudes changed-->celebrate; 2) price risen-->alaries not kept pace

所以 salaries kept pace-->price not rise-->stores not decrease

[此贴子已经被作者于2005-9-17 4:54:18编辑过]

作者: snowjing 时间: 2005-9-17 05:23

想了一会,觉得不可以.因为:

A-->B1+B2, 其等价逆否命题为(~B1)(~B2)-->(~A)

所以还要加上attitute changed, 才可以得出store not decrease.

大家不用回答上面的问题啦.

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