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GMATPrep Question Help

by span20 » Tue Aug 25, 2009 3:28 pm
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


OA: (B)

Can anyone explain to me why it's (B) and not (E)?
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Source: — Data Sufficiency |
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by grockit_jake » Tue Aug 25, 2009 4:02 pm
The key part to this question is that there is 1 kg total coffee, meaning x + y = 1.

x + y = 1

7.3 = 6.5x + 8.5y

Can be solved to give you a definite answer for x, since there are 2 variables and 2 equations.

Here I used the extreme of C=7.3. Make sure to plug in another value (say, C=8) to test for consistency.
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