一题逻辑题：For similar cars and drivers, automobile insurance for collision damage ha

yunduanxw

For similar cars and drivers, automobile insurance for collision damage has always cost more in Greatport than in Fairmont. Police studies, however, show that cars owned by Greatport residents are, on average, slightly less likely to be involved in a collision than cars in Fairmont. Clearly, therefore, insurance companies are making a greater profit on collision-damage insurance in Greatport than in Fairmont.


Which of the following is an assumption on which the argument depends?
A. Repairing typical collision damage does not cost more in Greatport than in Fairmont.
B. There are no more motorists in Greatport than in Fairmont.
C. Greatport residents who have been in a collision are more likely to report it to their insurance company than Fairmont residents are.
D. Fairmont and Greatport are the cities with the highest collision-damage insurance rates.
E. The insurance companies were already aware of the difference in the likelihood of collisions before the publication of the police reports.


答案都说是A：我也能理解，但是我认为这个答案是有问题的
我的推理过程如下：

For similar cars and drivers, automobile insurance for collision damage has always cost more in Greatport than in Fairmont.
以下的假设是满足了题目的要求的，即：
Greatport = G        单车保费：150
Farimont = F         单车保费：100

residents are, on average, slightly less likely to be involved in a collision than cars in Fairmont.
以下的假设是满足了题目的要求的，即：
Greatport = G       有10辆车        be involved in collision的车有1辆      出险率是10%
Farimont = F        有10辆车        be involved in collision的车有2辆      出险率是20%

假设A是答案：
我们取反：Repairing typical collision damage does not cost more in Greatport than in Fairmont.
Greatport = G        单车陪费：12
Farimont = F         单车陪费：10

结论：
Greatport = G        profit = 10*150 – 1*12 = 1476
Farimont = F         profit = 10*100 – 2*10 = 980

很明显G的利润1476 > F的利润980

取反后，还是没有颠覆原文的结论：insurance companies are making a greater profit on collision-damage insurance in Greatport than in Fairmont.

只有取反后，颠覆原文结论才能是原文的隐含假设，现在取反后，原文结论依然成立，所以A是不对的。可全世界的人都说A是正确答案，连manhattangmat的大师RonPurewal也是这么说的：
the problem takes "less likely to be involved in a collision" and treats it as equivalent to "less money paid out in collision claims". (they must be making this connection in order to reach the given conclusion re: profit.)
the assumption in choice (a) is necessary for us to make this connection. i.e., if there's a possibility that greatport's accidents are more destructive (and therefore more expensive) than fairmont's, then the connection is severed and the argument no longer works.

我的推理错在哪里呢？请高手解答一下！谢谢！

alaleiLALA

额，私以为这题是不用考虑具体数字的。因为带入数字不同，结果是不同的。只需要考虑修理费G大于F时，利润有可能F比G高就可以了。这题就做完了。

安徽民工

OG上的选项于此不同，但是问题相同，而且OG的解释也是从单件事故的损失入手的。

Aaroncy

lz！og上面的选项请你仔细看一下  和你贴出的选项是不同的。你贴的这题选A没错，和OG上的这题的答案是对应的，只是OG是B。

yunduanxw

顶！

yunduanxw

顶！

yunduanxw

自己顶！

yunduanxw

A is the answer.

Profit = Insurance premium - repair cost.

If repair cost is high, profit will be lowered.

-- by 会员 sdcar2010 (2011/11/27 22:18:08)

你这个公式太对了，你没看我的分析.
repair cost high 了，insurance premium 更high，你说profit be lowered or be heightened ?
题目并没有限定“insurance premium 不可以更high”

sdcar2010

A is the answer.

Profit = Insurance premium - repair cost.

If repair cost is high, profit will be lowered.

yunduanxw

顶！