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Source: — Data Sufficiency |

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by [email protected] » Sun Aug 31, 2014 9:51 pm
HI abhasjha,

In certain DS questions, the answer to the question is hidden behind some "math fat." By doing some basic algebra, the exact answer to the question can be found "hidden" in a given Fact.

Here, we're asked if Y < 2X. This is a YES/NO question.

Fact 1: Y/4 < X/2

Here, we can multiply both sides by 4....

Y < 2X

Now we KNOW that Y < 2X, so the answer to the question is ALWAYS YES.
Fact 1 is SUFFICIENT

Fact 2: (Y-2X)/3 < 0

Again, a bit of algebra will simplify this inequality....multiply both sides by 3

Y - 2X < 0

Y < 2X

Here, we also KNOW that Y < 2X, so the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT

Final Answer: D

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Rich
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by Brent@GMATPrepNow » Tue Sep 02, 2014 7:40 am
abhasjha wrote:Is y < 2x?

(1) y/4 < x/2

(2)(y - 2x)/3 < 0

Target question: Is y < 2x? (YES/NO question)

Statement 1: y/4 < x/2
Eliminate the fractions by multiplying both sides by 4 to get: y < 2x
PERFECT! This matches the question our target question is asking.
So, YES, it is definitely the case that y < 2x
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: (y - 2x)/3 < 0
To analyze this statement, we can use something I call The Something Method (free video here: https://www.gmatprepnow.com/module/gmat- ... ing?id=988)
So, this statement tell us that (something)/3 < 0
3 is a positive #, so we have: (something)/(positive #) < 0
This tells us that something is NEGATIVE
So, something < 0
This means y - 2x < 0
Add 2x to both sides to get y < 2x
PERFECT! This matches the question our target question is asking.
So, YES, it is definitely the case that y < 2x
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent
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by GMATinsight » Tue Sep 02, 2014 10:11 pm
abhasjha wrote:IS y<2x

(1) y/4<x/2

(2)( y-2x)/3 <0
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