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标题: 请教gwd-26-31 [打印本页]

作者: woodlittle 时间: 2009-4-29 07:34 标题: 请教gwd-26-31

Q31:

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.

作者: lixinli 时间: 2009-4-29 20:53

隐含有个条件x+y《=1(不然感觉没法做，理由是质量守恒吧）变形下，y<=1-x,根据条件2，7.3<=c=6.5x+8.5y<=6.5x+8.5(1-x)=8.5-2x最后得出x<=0.6.必然比0.8小了。

而根据条件1，只能得出x<0.85.所以选b

作者: woodlittle 时间: 2009-4-30 06:47

是自己粗心了，谢谢楼上的解答！

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