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Absolute Value - Confused

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Absolute Value - Confused

by Maysaa » Fri May 30, 2014 6:08 am
Hi everyone,

I am generally confused when it comes to absolute values in DS :cry: , 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: — Data Sufficiency |
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by theCodeToGMAT » Fri May 30, 2014 8:30 am
Did you forget to upload the question?
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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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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.

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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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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 √4 is equal to 2 or -2, we could really say:
√4 = |2|

That's why when you see (√x)², you shouldn't just interpret that as x. You should interpret (√x)² = |x|.

If we know that x² > y², 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.
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