coffee blend

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gmat009: Master | Next Rank: 500 Posts; Posts: 458; Joined: Sun Aug 31, 2008 10:44 amFollowed by: 1 member; Thanked: 3 times

by gmat009 » Wed Oct 01, 2008 9:51 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
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 sufficie

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Source: Beat The GMAT — Data Sufficiency | Wed Oct 01, 2008 9:51 pm

jeffxujian: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Sun Aug 24, 2008 1:24 am; Location: LA; Thanked: 2 times; GMAT Score:740

by jeffxujian » Wed Oct 01, 2008 10:31 pm

OA should be B right?

Based on the original condition, we can derive the following few things:
1. X+Y = 1 and the equation C=.........
now let's evaluate each condition,
1. Y >.15 Since we know that X+y=1 we can derive that X=1-y or y=1-x. In this case we want X=1-y. Because Y is greater than .15 we have almost unlimited number of alternatives for X, x is .7 when Y is .3, x is .81 when Y is .19, therefore, the condition is insufficient because it leaves too many possibilities.
2. since we have a approximate value of C, we can substitute the y in the original equation with 1-x--> C=6.5X+8.5*<1-X> is greater than or equal to $7.30. then you will get X <=.6 which is sufficient enough to answer the question.

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gmat009: Master | Next Rank: 500 Posts; Posts: 458; Joined: Sun Aug 31, 2008 10:44 amFollowed by: 1 member; Thanked: 3 times

by gmat009 » Thu Oct 02, 2008 8:20 am

jeffxujian wrote:OA should be B right?

Based on the original condition, we can derive the following few things:
1. X+Y = 1 and the equation C=.........
now let's evaluate each condition,
1. Y >.15 Since we know that X+y=1 we can derive that X=1-y or y=1-x. In this case we want X=1-y. Because Y is greater than .15 we have almost unlimited number of alternatives for X, x is .7 when Y is .3, x is .81 when Y is .19, therefore, the condition is insufficient because it leaves too many possibilities.
2. since we have a approximate value of C, we can substitute the y in the original equation with 1-x--> C=6.5X+8.5*<1-X> is greater than or equal to $7.30. then you will get X <=.6 which is sufficient enough to answer the question.

It is indeed B. Thanks

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