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题库 / Prep2007E2-DS-7
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 ~$\geq $~ 7.30
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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（1）知道 x+y=1之后可以很快推出y=1-x，代入到y>0.15中得出1-x>0.15，得x<0.85，x可以取0.84,0.83等大于0.8的值，亦可以取0.79，0.78等小于8的值。不充分
（2）C=6.5X+8.5Y>7.3, 代入y=1-x，得到6.5X+8.5（1-x）=8.5-2X>7.3，X<0.6， 在数轴上0.6在0.8的左边，故充分。
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