One kilogram of a certain coffee brand consists of x kilograms of Type I coffee and y kilograms of Type II coffee. The cost of the brand is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8?
1) y >= 0.15
2) C >= 7.30
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- Harish Dorai
- shaji
Re: GMATPrep(TM) - Practice Test 2 - DS#31
x+y=1
Statement 1 implies that x could be less, equal or more than 0.8; not sufficient.
Statement 2 certainly is.
The correct answer is B
Statement 1 implies that x could be less, equal or more than 0.8; not sufficient.
Statement 2 certainly is.
The correct answer is B
Harish Dorai Wrote:One kilogram of a certain coffee brand consists of x kilograms of Type I coffee and y kilograms of Type II coffee. The cost of the brand is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8?
1) y >= 0.15
2) C >= 7.30
- StaceyKoprince
- ManhattanGMAT Staff
- Posts: 9355
- Joined: Wed Oct 19, 2005 9:05 am
- Location: Montreal
x + y = 1
If y>=0.15, then try some:
If y=0.15, x = 0.85 in which case, no, x is not less than 0.8.
If y=0.3, then x=0.7, in which case, yes, x is less than 0.8.
Contradictory answers = indufficient.
y = 1-x
If C >=7.30, then try some:
If C=7.30, then 7.3 = 6.5x + 8.5(1-x)
7.3 = 6.5x + 8.5 - 8.5x
-1.2 = -2x
1.2/2 = x
x = 0.6, so yes, x < 0.8.
What happens if I increase C? I can either try a larger number or use logic to figure out if x will go up or down - totally up to you on the real thing.
If x+y=1, and I need to create a larger C, I have to make x smaller and y larger (because I multiply y by 8.5 in the formula while only multiplying x by 6.5). So, x will decreas as C increases. As a result, I can always say that x < 0.8. Sufficient.
If y>=0.15, then try some:
If y=0.15, x = 0.85 in which case, no, x is not less than 0.8.
If y=0.3, then x=0.7, in which case, yes, x is less than 0.8.
Contradictory answers = indufficient.
y = 1-x
If C >=7.30, then try some:
If C=7.30, then 7.3 = 6.5x + 8.5(1-x)
7.3 = 6.5x + 8.5 - 8.5x
-1.2 = -2x
1.2/2 = x
x = 0.6, so yes, x < 0.8.
What happens if I increase C? I can either try a larger number or use logic to figure out if x will go up or down - totally up to you on the real thing.
If x+y=1, and I need to create a larger C, I have to make x smaller and y larger (because I multiply y by 8.5 in the formula while only multiplying x by 6.5). So, x will decreas as C increases. As a result, I can always say that x < 0.8. Sufficient.
Stacey Koprince
Instructor
Director, Content & Curriculum
ManhattanPrep
Instructor
Director, Content & Curriculum
ManhattanPrep
- jatin
- Students
- Posts: 2
- Joined: Thu Feb 23, 2012 8:26 pm
Re: One kilogram of a certain coffee brand consists of x
Hi Stacey!
I have a doubt. Why are you considering x+y=1?
It is never written in Q stem that these are only 2 components.
For example, z kg of water, which is free of cost, can be present. Therefore, the cost of water is not included.
Is my understanding correct?
I have a doubt. Why are you considering x+y=1?
It is never written in Q stem that these are only 2 components.
For example, z kg of water, which is free of cost, can be present. Therefore, the cost of water is not included.
Is my understanding correct?
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
Re: One kilogram of a certain coffee brand consists of x
the statement "xxxx consists of A and B" means that xxxx consists of A and B.
there are other words that would permit "unknown other things" as well (e.g., "includes")... but not "consists".
there are other words that would permit "unknown other things" as well (e.g., "includes")... but not "consists".
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
Re: One kilogram of a certain coffee brand consists of x
also, MUCH more importantly, there are NEVER any "trick questions" on this exam.
never ever ever ever ever.
• the words always mean what they say. also, they don't mean what they don't say.
(this is enough to settle your question above)
• the statements will always mean whatever they would mean to %99.9 of people walking down the street.
• if you come up with a "aha! tricky! got you!" possibility, ignore it.
that's not how this test works.
never ever ever ever ever.
• the words always mean what they say. also, they don't mean what they don't say.
(this is enough to settle your question above)
• the statements will always mean whatever they would mean to %99.9 of people walking down the street.
• if you come up with a "aha! tricky! got you!" possibility, ignore it.
that's not how this test works.
6 posts Page 1 of 1