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题库 / Prep2007E2-DS-76
Over a certain time period, did the number of shares of stock in Ruth's portfolio increase?
(1) Over the time period, the ratio of the number of shares of stock to the total number of shares of stocks and bonds in Ruth's portfolio increased.
(2) Over the time period, the total number of shares of stocks and bonds in Ruth's portfolio increased.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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默认portfolio只含有s b
(1) Over the time period, the ratio of the number of shares of stock to the total number of shares of stocks and bonds in Ruth's portfolio increased.
(2) Over the time period, the total number of shares of stocks and bonds in Ruth's portfolio increased.
S/S+B增大，S+B增大——>S一定增大，选C
（1）S/B增大 （2）S+B增大， 两条件单独都不知道B是不是增大
为什么不考虑变化的幅度？也有可能S和B都增大了，但是S增大的幅度比B大，那样的话，两条件和起来也不能得出B是否增大
1） S/ S+B 变大 2） S+B 变大 综合1）+2） 如果S+B 变大，只能是S 变大
第一个条件得到ay>bx;
第二个条件得到a+b>x+y;
分析：要同时满足上述条件，则当bx; 当b>y,有a>x
没审题，（1）a/b大了，不能证明什么，（2）b大了，但是也不行
联立的，话，b大了，证明a也大了