10.19 Gmat官网数学题

JJJ.

题目如下：
From May 1, 1960, to May 1, 1975, the closing price of a share of stock X doubled. What was the closing price of a share of stock X on May 1, 1960 ?

(1)From May 1, 1975, to May 1, 1984, the closing price of a share of stock X doubled.

(2)From May 1, 1975, to May 1, 1984, the closing price of a share of stock X increased by $4.50.

答案是“BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.”
给出的解释是“Neither statement (1) alone nor statement (2) alone gives any information about the price from 1960 to 1975. Thus, the answer must be C or E. From statements (1) and (2) together, the closing price of a share of the stock on May 1, 1975, can be determined ($4.50) and the closing price on May 1, 1960, can be determined (half of $4.50). Therefore, (1) and (2) together are sufficient, and the best answer is C. ”

那么疑问来了...
（2）说的是by $4.50，意思不是说上升幅度是4.50，那怎么能算出1960的价格？
默默觉得答案的解释给人感觉是to $4.50（上升到4.5），所以可以算出来。

是我哪里看错了嘛？

jasminsword

increase by 是说增加了4.5，如果两个条件加一起，就是说同时翻倍了，那么一倍就是4.5，所以1975的价格也就是4.5，同理，1960的价格就是4.5的一半，2.25

JJJ.

jasminsword 发表于 2015-10-19 13:27
increase by 是说增加了4.5，如果两个条件加一起，就是说同时翻倍了，那么一倍就是4.5，所以1975的价格也就 ...

!! 明白了~~谢谢！