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标题: 求解一道GWD数学题！！！！！！！！！！！！！ [打印本页]

作者: zjhzkingsam 时间: 2011-5-19 06:55 标题: 求解一道GWD数学题！！！！！！！！！！！！！

One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee.  The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y.  Is x < 0.8?
(1)    y > 0.15
(2)    C ≥ 7.30

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
答案是B    求做法！！！！！！！！！！

作者: zhaoyiqing 时间: 2011-5-19 21:35

由题目暗示可知 X+Y=1 所以C=6.5X+8.5Y可以转化为 C=8.5-2X，代入问题则问题X<0.8就可以转化为C>6.9。所以只与C的大小有关，所以选B

作者: newolder 时间: 2011-5-20 06:41

有个隐含条件 X+Y=1

作者: imbalancey 时间: 2011-5-23 06:27

我也一直有疑问谢谢啦

作者: legnawen 时间: 2011-5-23 20:19

由（2）可推出Y大于等于0.4，而X+Y=1，则Y小于等于0.6. 肯定是小于0.8了

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