感觉比较难的一道逻辑题，请NN帮忙看看。

hermit127 · 发表于 2010-5-5 17:50:48

The organizers of tomorrow's outdoor concert announced that it will go on tomorrow on schedule unless bad weather is forecast or too few advance tickets are sold. If the concert is cancled, refunds will be made to ticket holders. Since some ticket holders have already been issued refunds even though more than enough advance tickets were sold, it must be the case that bad weather is forecast.

Which of the following is an error of reasoning contained in the argument?

A), It proceeds as if a condition, which by it self is enough to guarantee a certain reuslt, is the only condition under which that result would occur.

B), It bases a conclusion that is known to require two conditions on evidence that bears on only one of those conditions.

C), It explains one event as being caused by another event, even though both events must actually have been caused by some third, unidentified event.

D), IT treats evidence for the absence of one condition under which a circumstance would occur as conclusive evidence that that circumstance will not occur.

E), Evidence given to support the conclusion actually undermines it.

hermit127 · 发表于 2010-5-5 18:08:42

如果A1表示bad weather，A2表示too few tickets,用B表示concert go on,用C表示refund可以得到，A1否+A2否-->B, B否-->C，但是逆命题C-->B否不成立，不知道分析的是否正确？谢谢！

hermit127 · 发表于 2010-5-5 18:14:10

原文里面“unless bad weather is forecast or too few advance tickets are sold”，OR应该是“或命题”，但是感觉只有A1否和A2否“与命题”才正确啊，因为只有“天气好”并且“票卖得好”，音乐会才能够继续。不知道哪里出错了？

hermit127 · 发表于 2010-5-5 18:15:22

另外正确答案是： A

逆水潜龙 · 发表于 2011-12-23 02:06:13

天气和售票为音乐会取消的必要条件，而音乐会取消是资金返还的充分条件。
题目说资金返回必要条件，无法推得充分条件音乐会取消。因为一个必要条件可以被很多个充分条件所“圈住”，（如主唱失踪也会导致其资金返回）除非如A所说，该音乐会取消是资金返回的唯一充分条件，所以他两会变为充要条件。即资金返回顺推音乐会取消再顺推天气差。
做这题最好画出箭头或者圈圈代表其顺推关系，要不很容易掉进GMAT的陷阱·

感觉比较难的一道逻辑题，请NN帮忙看看。

所属分类: GMAT考试

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