Absolute Value - Confused - The Beat The GMAT Forum - Expert GMAT Help & MBA Admissions Advice

Absolute Value - Confused

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Maysaa: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon May 12, 2014 5:53 pm; Location: United Arab Emirates

by Maysaa » Fri May 30, 2014 6:08 am

Hi everyone,

I am generally confused when it comes to absolute values in DS

, however this post by ManhattanGMAT's didn't really help, why is statement 1 sufficient?

[url]https://www.beatthegmat.com/mba/2010/12/ ... ue-problem

Is |x|>|y|?

(1) (x^2) > (y^2)

(2) x > y

I understand why statement 2 is insufficient, but I don't understand why statement 1 is sufficient when we plugged in x=2 and y=-3 and got a NO to our question?

Can anyone please explain?

Thank you

Maysaa

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Source: Beat The GMAT — Data Sufficiency | Fri May 30, 2014 6:08 am

theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Fri May 30, 2014 8:30 am

Did you forget to upload the question?

R A H U L

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Maysaa: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon May 12, 2014 5:53 pm; Location: United Arab Emirates

by Maysaa » Fri May 30, 2014 10:40 pm

Hi Rahul,

Thanks for this - for some reason I can see the question but when I hit send it doesn't show.

Anyway - I am trying to improve my DS skills and I am particularly confused when it comes to absolute value. I tried to review an article by ManhattanGMAT with regards to the following question:

Is |x|>|y|?

(1) (x^2) > (y^2)

(2) x > y

I can understand why ST2 is not sufficient but I don't understand how ST1 is found sufficient when we can input a value of x = 2 and y=-3 and it wouldn't be applicable.

Thanks for helping out!

Maysaa[/url]

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GMAT/MBA Expert

[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Fri May 30, 2014 11:08 pm

Hi Maysaa,

In a DS question, each statement is essentially factual information that you're supposed to use to answer the question.

In Fact 1, we're told that (X^2) > (Y^2).

Your example (X = 2, Y = -3) does NOT fit the given information, so you are NOT allowed to use that example. You COULD use (X = -3, Y = 2); these numbers will give you a YES answer to the given question. Any combination of values that fits the information in Fact 1 will also give you a YES answer to the question. The consistent answer is what makes Fact 1 SUFFICIENT.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Maysaa: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Mon May 12, 2014 5:53 pm; Location: United Arab Emirates

by Maysaa » Fri May 30, 2014 11:22 pm

Thanks Rich.

I think I made the rookie mistake of carrying over information from one statement to the other!

Thanks again,
Maysaa

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GMAT/MBA Expert

ceilidh.erickson: GMAT Instructor; Posts: 2095; Joined: Tue Dec 04, 2012 3:22 pmFollowed by: 247 members; Thanked: 1443 times

by ceilidh.erickson » Sat May 31, 2014 8:33 am

Absolute value and squares are often related. Think about a square root: if we say that âˆš4 is equal to 2 or -2, we could really say:
âˆš4 = |2|

That's why when you see (âˆšx)Â², you shouldn't just interpret that as x. You should interpret (âˆšx)Â² = |x|.

If we know that xÂ² > yÂ², we don't know whether they are positive or negative, but it doesn't matter. If the square of one number is greater than the other, that number must be further from 0.

Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education

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