求助 狒狒逻辑 70题

tmacking

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

答案是c  
个人怎么觉得是b啊  知道70%的低气压导致降雨  又根据b知道降雨中雷阵雨的概率   相乘不就是结论吗    希望大家给点帮助 小弟完分感谢

huangyouhuifei

同问~~~

tmacking

大家帮帮忙 顶下

sdcar2010

Not all rainfalls come from low-pressure weather system.

neverlandlin

sdcar2010大牛，能再说的详细点吗？
这道题目实在不明白，为什么选C呢？
C说雷阵雨里面多少由低压导致，怎么能推出结论呢？不明白啊，NN们快来啊～

sdcar2010

I took it back. Answer B is right.

thechooosenone

同问~我也选的B~
rainfalls的概率*thundershowers占rainfalls比率=答案
怎么想怎么是B~
选c就没rainfalls啥事儿了~
为什么啊~答案有问题吧！

whopawo

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.

问的是由low-pressure systems 导致的thundershowers。不是问rainfalls中有多少thundershowers。
有可能rainfalls还不是由low-pressure systems 导致的呢。

steve_chem

同觉得   C根本推不出来

jaze

(B) the percentage ofspring rainfalls in Plainville that are thundershowers

P (thundershowers) = P (rainfall) * P(thundershower/rainfall)



(C) the percentage of thundershowers inPlainville that result from low-pressure systems

read carefully, what we can get from this option is that some thundershowers result from low-pressure systems
we can not get the possibility that low-pressure systems result in thundershowers