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# Is x-y>0?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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22 Sep 2016, 17:25
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Difficulty:

25% (medium)

Question Stats:

74% (00:42) correct 26% (00:46) wrong based on 47 sessions

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Is x - y > 0?

(1) x > |y|
(2) y = -3

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22 Sep 2016, 17:45
1.The magnitude of x is greater than y. Even if y is negative, the expression x-y will yield a positive answer. Hence this alone is sufficient.

2. Taking y = -3, without knowing the value of x is not enough to determine the value of the expression x-y. If x = -4, x-y is not greater than 0, whereas if x > -3 this yields a positive number. Hence, this alone is not sufficient !

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22 Sep 2016, 20:33
MathRevolution wrote:
1) x>|y|
2) y=-3

MathRevolution

I am unable to find the question asked for given options..
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23 Sep 2016, 05:47
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Top Contributor
MathRevolution wrote:
Is x - y > 0?

(1) x > |y|
(2) y = -3

Target question: Is x - y > 0?

This is a good candidate for rephrasing the target question.

Aside: Here’s a video with tips on rephrasing the target question: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1100

Take x - y > 0 and add y to both sides to get: x > y?

REPHRASED target question: Is x > y?

Statement 1: x > |y|
First, we know that |y| is greater than or equal to zero.
So, this statement tells us that x is POSITIVE

Second, |y| denotes the MAGNITUDE of y. That is, |y| is y's distance from 0 on the number line.
So, if x > |y|, then this tells us that the MAGNITUDE of x is greater than the MAGNITUDE of y
Since we also know that x is POSITIVE, we can be certain that x > y
Since we can answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT

Statement 2: y = -3
We have no information about x, so there's no way to determine whether x > y. So, statement 2 is NOT SUFFICIENT.

Cheers,
Brent
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23 Sep 2016, 10:24
The equation x-y>0 will be true only if x>y

Statement 1: x>|y| means x has to be positive and greater that y so sufficient
Statement 2 : y=-3 (x could be -4 or x could be 4 so insufficient)
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24 Sep 2016, 22:14
==> In the original condition, the variables become 2(x,yn) and C is also an answer, but since it is a absolute value question with key question, if you apply CMT 4(A)
In the case of 1), x>|y|>=-y always leads to x>-y, x+y>0 hence yes at all time, it is suffi. Thus, the answer is A.

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
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23 Feb 2017, 05:42
PROMPT ANALYSIS
x and y are the real numbers.

Superset
The answer could be either yes or no

Translation
In order to find if x>y, we need:
1# the exact value of x and y
2# any characteristics or relation which can help to deduce the answer.
STATEMENT ANALYSIS

St 1: x>|y|. Take values like y = 4 and -4 for which the value of x will be > 4. Hence x will always be greater than y. The statement will hold true SUFFICIENT. Option b,c and e eliminated.
St 2: y = -3. Doesnt really give any constraint for x. INSUFFICIENT. OPtion d eliminated

Option a
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Re: Is x-y>0? &nbs [#permalink] 23 Feb 2017, 05:42
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