gmat prep question

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yvonne12
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Topic: gmat prep question
PostWed Apr 25, 2007 12:31 pm
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if y>0 what is the value of X?

1. Ix-3I > y

2. Ix-3I < -y

please explain to me, how one would approach this kind of question
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jayhawk2001
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PostWed Apr 25, 2007 9:33 pm
yvonne12 wrote:
if y>0 what is the value of X?

1. Ix-3I > y

2. Ix-3I < -y

please explain to me, how one would approach this kind of question
Basic idea is that a modulus of a number can only be positive.

I recall seeing this question earlier and the second option was
|x-3| <= -y. I think you have left out the "=" part in 2.

1 - insufficient. x-3 > 0 implies x> 3. No unique value

2 - sufficient. |x-3| cannot be < 0. So it can only be = 0. So x = 3

Hence B.
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yvonne12
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PostWed Apr 25, 2007 10:08 pm
honestly I dont get it,why can't Ix-3I be negative? I dont understand absolute values in these kinds of problems... could you perhaps elaborate some more about these kinds of questions..I would appreciate it, since my test is on saturday and who knows if I might see this kind of question...


BTW, are you a monitor or someone that is also studying for the GMAT?. You have been answering all the questions I've been throwing out there, not that I have a problem with it...just curious. Im wondering how you know all this stuff. I've been studying for this exam for the past several months and even though I've been scoring high on the gmat prep, I still worry about this saturday (test day)....
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jayhawk2001
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PostWed Apr 25, 2007 10:28 pm
yvonne12 wrote:
honestly I dont get it,why can't Ix-3I be negative? I dont understand absolute values in these kinds of problems... could you perhaps elaborate some more about these kinds of questions..I would appreciate it, since my test is on saturday and who knows if I might see this kind of question...
If you have OG-11, please check page 126 section 9.

The absolute value of x, denoted by |x| is defined to be x if x>=0
and -x if x < 0.

Either way, |x| is positive. Basically modulus of x is the absolute
distance between x and 0 on the number line. This value is
always positive just like distances Smile.

I've seen 3 main concepts on GMATprep and other materials with
respect to modulus --

1. Finding value of -x|x|. This is simple if you know that |x| is always
positive and so the sign of -x determines the end result.

2. |x+y| <= |x| + |y|

3. Finding the value or range of |x - n |. In this case, you'll have to
assume that the "value" of x-n is always positive.

Now, if x is negative, x-n is negative and this is not permitted as
per modulus. So, |x-n| now becomes -(x-n)

If x is positive (and greater than n), |x-n| = x-n

I hope this helps.

yvonne12 wrote:
BTW, are you a monitor or someone that is also studying for the GMAT?. You have been answering all the questions I've been throwing out there, not that I have a problem with it...just curious. Im wondering how you know all this stuff. I've been studying for this exam for the past several months and even though I've been scoring high on the gmat prep, I still worry about this saturday (test day)....
I'm just a member trying to learn and help wherever I can. Haven't
taken the GMAT yet - so I'm still in learning mode Smile.

Good luck with your exams and hey give it your best shot !
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f2001290
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PostThu Apr 26, 2007 7:21 am
hi yvonne

i feel that sth is wrong with 2nd statement.

Modulus is always positive. So |X-3| cannot be <= -y;

Could you please check out the statemnet again.

All the best for your exam.
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