【求助！】关于Bible上的一题，numbers and percentage

Yui1991 · 发表于 2013-5-8 11:59:19

Ditrama is a federatin made up of three autonomus regions. Korva. Mitro, and Guadar, Under the federal revenue-sharing plan, each region receives a share of federa revenues equal to the share of the total population of Ditrama residing in that region as shown by a yearly populatin survey Last year the percentage of federal revenues Korva received for its share deereased somewhat even though the population surve on which the revenue-sharing was based showed that Korva s population had increased

If the statements above are true, which one of the following must also have been shown by the population survey on which last year s revenue-sharing in Dirama was based?

(A) Of the three regions Korva had the smallest number of residents
(B) The population of Korva grew by a smaller percentage than it did in previous years
(C) The populations of Mitro and Guadar each increased by a percentage that exceeded the percentage by which the population of Korva mcreased.
(D) Of the three regions. Korva s numerical inerease in population was the smallest
(E) Korva s population grew by a smaller percentage than did the population of at least one of the other two autonomous regions.

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数值这一章理解起来很容易啊~不过一做起题就容易脑子犯糊涂，各种绕= =文科生伤不起

Bible给出的答案是E ，说C错误的原因是两个都人数比都超过肯定是对的“Mitro and Guadar each increased by a percentage that exceeded”must be true
                                                         但是没有必要两个都超过 "it does not have to be true that both exceed Korva”，然后给了一个表举例说明了下：

                                                                                                                                            before                               after
                                                         Total population of Ditrama                                     30(100%)                                     100(100%)

                                                            population of Korva                                              10(33%)                                     15(15%)
                                                            (people/percent of total)
                                                            population of Mitro                                                 10(33%)                                     10(10%)
                                                            (people/percent of total)
                                                            population of Guadar                                              10(33%)                                     75(75%)
                                                            (people/percent of total)

                                                         说是通过以上的表，只有一个地区的人口增长超过了K就让K虽然人口数上升，但比例下降因此revenue比也下降，所以C是错的。

可是，我也举了个例：

                                                                                                                                         before                               after
                                                         Total population of Ditrama                                     10(100%)                                     100(100%)

                                                            population of Korva                                              3(30%)                                        40(40%)
                                                            (people/percent of total)
                                                            population of Mitro                                                 3(30%)                                        50(50%)
                                                            (people/percent of total)
                                                            population of Guadar                                              4(40%)                                        10(10%)

                                                            这样也满足了只有一个地区的人口增长超过了K地，但是K地占的比例也超过了之前，因此按stimulus里说的revenue比例和人口
                                                            比例一样来说的话“ each region receives a share of federa revenues equal to the share of the total population of
                                                            Ditrama residing in that region”，revenue也应该超过以前。

                                                            但是stimulus里的结果确是相反的，所以以上关于只需要一个地区的人口增长超过K地的假设不能保证人口上升但人口比一定下
                                                            降的说法不是不对么？
                                                            所以E项不是错的么？



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求牛牛们解答~~~~就快要考试了= =我也搞不明白，可能例子我就举错了？不过实在是脑子绕了我也看不出哪儿有问题....

Yui1991 · 发表于 2013-5-8 13:06:24

顶一个~~~~~~~·

花染水凉 · 发表于 2013-5-8 19:39:55

我觉得C的范围小于E，即C对了E一定对，但是E对了C不一定对。
at least the increase in population of one region exceeds that of K 可以是只有一个地区超过，或者是两个地区都超过。你举得反例恰恰也是属于E的范围内的。

而C选项中，它说另外两个地区都要同时超过K，即排除了只有一个地区超过K就可以使K总人口所占比例减少的可能性，即官方答案中给出的例子，所以它缩小了可能性。

Yui1991 · 发表于 2013-5-9 09:54:05

花染水凉发表于 2013-5-8 19:39
我觉得C的范围小于E，即C对了E一定对，但是E对了C不一定对。
at least the increase in population of one ...

嗯嗯~~我后来又想明白了.... 是从stimulus推出answer，我用answer去反推了stimulus不成立，但是原命题成立否命题不一定成立....有点充分必要性没搞明白。

谢谢解答~~~~

【求助！】关于Bible上的一题，numbers and percentage

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