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xuxu · 发表于 2003-9-17 02:29:00

21. A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.
Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?
(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do near by towns

Why is the correct B (where there is no mentioning of 'low-pressure system' thinng) instead of C?

?14. Either Perry’s faction or Tucker’s faction, but not both, will win control of the government. If Perry’s faction wins, the nation will suffer economically. If Tucker’s faction wins, the nation will suffer militarily.

Given the statements in the passage, which one of the following statements must be true?
(A) It is possible, but not certain, that the nation will neither suffer economically nor suffer militarily.
(B) If the nation suffers economically, it is certain that Perry’s faction has won control of the government.
(C) It is certain that the nation will suffer either economically or militarily, and also certain that it will not suffer both.
(D) If the nation suffers militarily, it is possible, but not certain, that Tucker’s faction has won control of the government.
(E) If the nation suffers both economically and militarily, it is certain that neither Perry’s faction nor Tucker’s has won control of the government.

Why D not C?

THANKS!!!

mindfree · 发表于 2003-9-17 03:20:00

I believe that both were explained before. Please check the prior posts before posting. It will help you because the explanation of those questions before might show you sth. you did not see.

1. You did not truly understand the question. Very often that ETS tests your understanding by giving a look-like choice.

Do the math here. We know that 70% chance the low pressure will cause rain fall.

B: We know the chance that rain fall will be thundershower. Let's assume it is 20%. Then the chance that the low pressure will cause thudershower is 70%*20%=14%

C: is irrelevant. You picked C because you either did not think too hard or you did not understand what C means. If we know that 50% of thundershowers are caused by low pressure, we still do not know th chance that low pressure will cause thundershowers.

2. This is the simple rule of reasoning. You made unwarranted assumptions yourself.

A-->B ==>not B-->not A. You made the assumption that A-->B ==>A-->not C. In the argument it is not mentioned that suffer economically and suffer militarily are exclusive. Do not make and assumptions unless it is common sense.

linchechin · 发表于 2004-4-24 21:54:00

Mindfree總教頭果然名不虛傳!!

番茄炒蛋 · 发表于 2004-4-24 22:55:00

呵呵，总教头得英文解释才是一级棒呢，坛子里没几个可以用E文解释得这么好得

dogdog · 发表于 2004-7-2 15:25:00

原来主要是对句意的准确理解：

C是有几成thundershowers是由l－p引起的。实际上仍然不知道多少l-p会引起thundershowers。

蓝色的心 · 发表于 2005-1-25 23:05:00

(C) the percentage of thundershowers in Plainville that result from low-pressure systems
谁能解释一下这个句子究竟应该怎么理解？

难道不是说：在P这个地方，由低气压导致雷阵雨的概率吗？

[此贴子已经被作者于2005-1-25 23:12:15编辑过]

mygoalusa · 发表于 2005-1-26 03:45:00

14. Either Perry’s faction or Tucker’s faction, but not both, will win control of the government. If Perry’s faction wins, the nation will suffer economically. If Tucker’s faction wins, the nation will suffer militarily.

Given the statements in the passage, which one of the following statements must be true?
(A) It is possible, but not certain, that the nation will neither suffer economically nor suffer militarily.
(B) If the nation suffers economically, it is certain that Perry’s faction has won control of the government.
(C) It is certain that the nation will suffer either economically or militarily, and also certain that it will not suffer both.
(D) If the nation suffers militarily, it is possible, but not certain, that Tucker’s faction has won control of the government.
(E) If the nation suffers both economically and militarily, it is certain that neither Perry’s faction nor Tucker’s has won control of the government.

Why D not C?

I will give it a try, to see if it makes sense. The question could be intepreted into this way:

P, not T; T, not P; P-->EcoSuffer; T-->MilSuffer

D. T-->MilSuffer ==> MiliSuffer-->T or MiliSuffer -\->T, no garantee if T will happen

C. Either T or P wins the election, so it is true that the nation will suffer either way, and also, POSSIBLY, both, if P wins control, the nation will EcoSuffer, which does not guarantee there is no MiliSuffer, becuase MiliSuffer is a necessary condition for T to happen, and T is sufficient condition for MiliSuffer to happen, which means something else could cause MiliSuffer to happen, not just T. And the stem does not say EcoSuffer and MiliSuffer cannot co-exist. Therefore, there is a possibility that the nation suffers both.

lawyer_1 · 发表于 2005-1-26 04:31:00

21题的C，注意PERCENTAGE是修饰thundershowers，即雷阵雨的多少比例是低压导致的。不是修饰low-pressure systems 。其实该题的关键是看PERCENTAGE修饰谁。

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