费费逻辑70

70. 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 determine 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  

 宝典解释：

参考答案：C

思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致；答案（C）给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。

A、  B没能和低压天气联系起来，D、E为无关选项

问题是下雷阵雨的概率。

个人认为：

下雷阵雨的概率＝下雨的概率（70％）×春雨中雷阵雨的概率（B）

若选C，雷阵雨中由于低气压造成的雷阵雨比率，那么我们是否需要知道下雷阵雨的概率才能计算

所以答案是否应该是B

参考答案：C

思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致；答案（C）给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。

A、  B没能和低压天气联系起来，D、E为无关选项

问题是下雷阵雨的概率。

个人认为：

下雷阵雨的概率＝下雨的概率（70％）×春雨中雷阵雨的概率（B）

若选C，雷阵雨中由于低气压造成的雷阵雨比率，那么我们是否需要知道下雷阵雨的概率才能计算

所以答案是否应该是B

 宝典解释：

参考答案：C

思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致；答案（C）给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。

A、  B没能和低压天气联系起来，D、E为无关选项

问题是下雷阵雨的概率。

个人认为：

下雷阵雨的概率＝下雨的概率（70％）×春雨中雷阵雨的概率（B）

若选C，雷阵雨中由于低气压造成的雷阵雨比率，那么我们是否需要知道下雷阵雨的概率才能计算

所以答案是否应该是B

参考答案：C

思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致；答案（C）给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。

A、  B没能和低压天气联系起来，D、E为无关选项

问题是下雷阵雨的概率。

个人认为：

下雷阵雨的概率＝下雨的概率（70％）×春雨中雷阵雨的概率（B）

若选C，雷阵雨中由于低气压造成的雷阵雨比率，那么我们是否需要知道下雷阵雨的概率才能计算

所以答案是否应该是B

我也覺得是B耶

誰能幫忙解釋一下答案為何是c呢

A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area.

加B，就可以得出概率

下雷阵雨的概率＝下雨的概率（70％）×春雨中雷阵雨的概率（B）

和文章紧密联系

而C最多得出雷雨中有低压引起的概率

还是认为不对

Prefer C

No coorelation of railfall and thunderstorm suggested in the text.[C] alone could build the most direct conneciton between thuderstorm % and low-pressure weather

Rainfall results from 70% of low-pressure weather system. (It could result from other weather systems too)

Thunderstorms (sometimes) result from low-pressure weather system (and sometimes result from others)

If we know (B) the percentage of spring rainfalls in Plainville that are thundershowers, P*0.70 is the probability that Plainville will have a thundershower (from this low-pressure system).

If we know (C) the percentage of thundershowers in Plainville that result from low-pressure system, we know directly the probability that Plainville will have a thundershower (from this low-pressure system).

If we know (A) the percentage of thundershowers in Plainville that occur in the spring, we know directly the probability that Plainville will have a thundershower soon

(A)其实给出的概率最完整，但太 general，没有提及low pressure system，也就是说，当我们看到有low pressure system，再算总体的概率比不上算有low pressure system导致的 thundershower 概率准确。

(B) 和 (C)得出是同一个概率，But 

 (B) is the only answer that has to be drawn from the original statement. Remember the question says “in addition to the information above".

（这也是又一个不选A的道理），题目说了要你结合原条件。

Therefore (B) is preferrable.