[梦之队日记] [自强不息队]-北京朝阳区2组GMAT复习日记

有阵子没上来了，今天一看，恭喜老吴！！！

今天去爬山之后，是不是又FB啦

我们后面的XDJM会加油的!

那我就不打算重考了。继续考托福吧。我前天问了一个今年申请到芝加哥大学的CDer，她GMAT也考了730分，作文也是4分，也建议我别再重考了。

跟大家说说我做的一道逻辑题吧,因为有意思才想拿出来分享.还记得那道

171. A recent report determined that although only three percent of drivers on Maryland
highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles
ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip
their vehicles with radar detectors are more likely to exceed the speed limit regularly than
are drivers who do not.
The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for
exceeding the speed limit than are drivers who do not.
(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the
speed limit regularly than are drivers who are not ticketed.
(C) The number of vehicles that were ticketed for exceeding the speed limit was greater
than the number of vehicles that were equipped with radar detectors.
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed
more than once in the time period covered by the report.
(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on
other state highways not covered in the report.

我第一次做时只是考虑找gap,没有仔细想,今天再碰到这题时,觉得有点意思,想好好算一下.我用数学概率语言解释一下:答案很容易判断

A事件代表配备雷达,B事件代表超速罚款

1. p(A)=3%

2. p(AIB)=33%

问是否p(BIA)>p(BIA)?

其实就是问p(BIA)>p(B)?因为p(B)在p(BIA)和p(BIA)之间

通过2.可以得出超速罚款的车中有雷达的可能型比没超速罚款的车要大,通过1.和2.还可以判断p(B)<1/11但不能判断比p(A)大还是小,这一结论于最后的问题无关,只是可以推断出的一个结论.属题外话.但要说有雷达的车容易超速被罚款就需要证明了,现在还不能马上推出结论.

问是否p(BIA)>p(B)

就是问p(AB)/p(A)>p(B)

就是问p(B)*p(AIB)/p(A)>p(B)

所以就是问p(AIB)/p(A)>1

显然>1

所以有雷达的车容易比没雷达的车容易超速罚款,而超速罚款的车更容易经常性超速,所以有雷达的车更容易比没雷达的车经常性超速.

A选项显然不对,说反了

C选项没法判断,因为p(B)和p(A)没法判断

DE毫无关系.

这题出的很严谨,很有意思!

能否现在申请加入，id：alice  目标：9月

希望能用MSN，对这里的各个链接都不是很熟啊：alice_1983_911(A) hotmail.com

希望能团体复习，有个小群方便讨论：）