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inequalities problem

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inequalities problem

by RaginT » Tue Jun 01, 2010 3:51 am
Hi all, I just completed a GMAT practice test (official test prep) and scored 700 so I'm very happy (real thing in 3 days time). However the following question stumped me:

Is x - y + 1 greater than x + y - 1 ?

1) x > 0

2) y < 0

The answer is (B) statement 2 alone is sufficient

Can anybody help?
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Source: — Data Sufficiency |
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by selango » Tue Jun 01, 2010 4:07 am
Lets rephrase it,

x-y+1>x+y-1

-->-y+1>y-1

-->2y<2 or y<1

From stmt 2 we know y<0 and it satisfy the above condition.

Hence B is sufficient.
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by pradeepkaushal9518 » Tue Jun 01, 2010 4:10 am
i have the same approach

congrts for scoring 700.

can u tell which books are u following and for how many days u are preparing for it.
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by Patrick_GMATFix » Tue Jun 01, 2010 4:34 am
Selango's explanation is great.

Is x-y+1 > x+y-1 ?
Subtract x --> Is -y+1 > y-1 ?
add y & 1 ---> Is 2 > 2y ?
REPHRASE ---> Is 0 > y?

The 1st statement tells you nothing about the sign of y, but the 2nd statement does. B is correct.

It should always be your instinct to simplify any equation you're given. Otherwise you are more likely to miss out on the information that it can convey. In DS, it's very important to rephrase the question when possible.This is GMATPrep question 1602. Watch a video solution if the explanation above isn't clear. If you struggle with inequalities, you can also use the Drill Engine to generate timed practice; set topic='Inequalities' and difficulty='600-700 AND 700+'

RaginT, good luck on your test!
-Patrick
  • Ask me about tutoring.
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by RaginT » Tue Jun 01, 2010 5:53 am
pradeepkaushal9518 wrote:
can u tell which books are u following and for how many days u are preparing for it.
Sure - I am using the Manhattan GMAT series. It took me 2 months just to go through all their mathematics books. For the last month I have been doing MGMAT CAT tests and official guide questions. My verbal score is already good, so I had to concentrate on math the most. I also used MGMAT turbocharge math questions - these are not as good quality as the official questions but are good practice nonetheless.

If I beat the GMAT on Friday I will post a detailed description of my study plan - keep an eye out!

Thanks to all who replied - it was actually quite an easy inequalities question and I failed to see that x could be eliminated from both sides - I think my brain is fried from too many CAT exams!!
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