一道逻辑题请教各位前辈

betty3608

刚刚看是备考GMAT，在看陈向东的逻辑推理。在下才疏学浅，有道题始终想不明白，想请教下各位前辈。

In 1985 a consumer agency concluded that Xylo brand bicycles are safer to ride than are Zenon brand bicycles. The agency based the conclusion on the ratio of the number of rider injuries to the number of riding hours for each brand of bicycle from 1981 through 1984. Yet for identically designed bicycles manufactured since 1985, the number of rider injuries has been twice as great among riders of Xylos as among riders of Zenons. Therefore, the agency's conclusion would have been different for the period  since 1985.

Which of the following is an assumption that, if true, supports the claim that the agency's conclusion would have been different for the period since 1985?

a) For the period since 1985, the number of riding hours for Zenons totaled at least half the number of riding hours for Xylos.

b) Of all the bicycles ridden in the period since 1985, the percentage of Xylos ridden was twice the percentage of Zenons ridden.

c) Prior to 1985, Zenon owners were more likely than Xylo owners to report the injuries they sustained  while riding their bicycles.

d) In 1985 the agency had miscalculated the ratior for Xylos, for Zenons, or for both.

e) Soon after the agency had issued its report, consumer demand for Xylos increased more rapidly than did consumer demand for Zenons.

看到有数字的就头疼。期待各位前辈的指点，给我讲讲做这道题的思考方法。

candycane13

是不是选A？

betty3608

对！正确答案是A！

为什么呢？

zliycwn1

他们是比这个ratio

受伤人数/总骑车时间

如果两个牌子都被骑了100小时，骑X伤了50个人，骑Y伤了1个，当然是Y安全

如果X被骑了100小时伤了50个，和Y被骑2小时而伤一个的情况下，X和Y相同

如果X伤者是Y伤者的两倍，只有在骑X时间是Y的两倍的情况下才能说两者一样安全

但如果Y被骑的时间少于X的一半，就说明是Y安全

betty3608

恩。谢谢你的解答。

原来真的是数学问题。不过你的最后一句话我还是有点疑惑呢~

按照比例，[X(伤者)/X(时间)] > [Z(伤者）/Z(时间)]

因为X(伤者)=2Z(伤者）  所以 X(时间)<2Z(时间）由此：Z时间>0.5X时间

应该说：是Z的时间至少是X的一半。

不知我说的对不对~还请指教。