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# Is |x| = y - z ? 1. x + y = z 2. x < 0

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Manager
Joined: 05 Feb 2007
Posts: 138
Is |x| = y - z ? 1. x + y = z 2. x < 0 [#permalink]

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28 Jan 2009, 08:23
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Is |x| = y - z ?

1. x + y = z
2. x < 0

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Senior Manager
Joined: 30 Nov 2008
Posts: 482
Schools: Fuqua
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 09:02
IMO A.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.
SVP
Joined: 17 Jun 2008
Posts: 1502
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 10:54
I think, answer should be C.

if x = 2, y = 3 and z = 5, then
from stmt1: 2 + 3 = 5.
Also, |x| = 2
and y - z = -2
Hence, |x| does not equal y - z

Similarly, if x = -2. y = -3 and z = -5
then |x| = 2
y - z = 2

And |x| = y-z.

Thus, in order for|x| = y-z to be true, both statements are required. Hence, C should be the answer.
SVP
Joined: 07 Nov 2007
Posts: 1756
Location: New York
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 10:58
scthakur wrote:
I think, answer should be C.

if x = 2, y = 3 and z = 5, then
from stmt1: 2 + 3 = 5.
Also, |x| = 2
and y - z = -2
Hence, |x| does not equal y - z

Similarly, if x = -2. y = -3 and z = -5
then |x| = 2
y - z = 2

And |x| = y-z.

Thus, in order for|x| = y-z to be true, both statements are required. Hence, C should be the answer.

OOPS!! missed -ve part.
_________________

Smiling wins more friends than frowning

Senior Manager
Joined: 30 Nov 2008
Posts: 482
Schools: Fuqua
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 12:14
scthakur wrote:
I think, answer should be C.

if x = 2, y = 3 and z = 5, then
from stmt1: 2 + 3 = 5.
Also, |x| = 2
and y - z = -2
Hence, |x| does not equal y - z

Similarly, if x = -2. y = -3 and z = -5
then |x| = 2
y - z = 2

And |x| = y-z.

Thus, in order for|x| = y-z to be true, both statements are required. Hence, C should be the answer.

My weak point in Quant is always DS and in specific it worst when they are related to Absolute values / Inequalities.

Can one of you please explain why my approach is wrong.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.

I know we can solve the DS questions by picking the numbers intelligently. But I am not able to rely on that process 100 %. So looking for alternate approaches on tackling DS questions.
SVP
Joined: 07 Nov 2007
Posts: 1756
Location: New York
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 13:09
mrsmarthi wrote:
scthakur wrote:
I think, answer should be C.

if x = 2, y = 3 and z = 5, then
from stmt1: 2 + 3 = 5.
Also, |x| = 2
and y - z = -2
Hence, |x| does not equal y - z

Similarly, if x = -2. y = -3 and z = -5
then |x| = 2
y - z = 2

And |x| = y-z.

Thus, in order for|x| = y-z to be true, both statements are required. Hence, C should be the answer.

My weak point in Quant is always DS and in specific it worst when they are related to Absolute values / Inequalities.

Can one of you please explain why my approach is wrong.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.

I know we can solve the DS questions by picking the numbers intelligently. But I am not able to rely on that process 100 %. So looking for alternate approaches on tackling DS questions.

statemet 1:
-X = Y - Z -->
we don't the whether X is +ve or -ve
assume X +ve then X= -Y+Z --> |X|=Z-Y ( answer No)
when x is -ve then -X= Y-Z --> |X|=Y-Z (answer Yes)
so not suffcieint

combine wiht stat2: X<0
it is suffcient.
_________________

Smiling wins more friends than frowning

Senior Manager
Joined: 02 Nov 2008
Posts: 255
Re: DS - Number Properties, Absolute Value [#permalink]

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28 Jan 2009, 23:28
x2suresh wrote:
mrsmarthi wrote:
scthakur wrote:
I think, answer should be C.

if x = 2, y = 3 and z = 5, then
from stmt1: 2 + 3 = 5.
Also, |x| = 2
and y - z = -2
Hence, |x| does not equal y - z

Similarly, if x = -2. y = -3 and z = -5
then |x| = 2
y - z = 2

And |x| = y-z.

Thus, in order for|x| = y-z to be true, both statements are required. Hence, C should be the answer.

My weak point in Quant is always DS and in specific it worst when they are related to Absolute values / Inequalities.

Can one of you please explain why my approach is wrong.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.

I know we can solve the DS questions by picking the numbers intelligently. But I am not able to rely on that process 100 %. So looking for alternate approaches on tackling DS questions.

statemet 1:
-X = Y - Z -->
we don't the whether X is +ve or -ve
assume X +ve then X= -Y+Z --> |X|=Z-Y ( answer No)
when x is -ve then -X= Y-Z --> |X|=Y-Z (answer Yes)
so not suffcieint

combine wiht stat2: X<0
it is suffcient.

Just keep in mind that with absolute values you are usually going to deal with 2 values (+/-)
SVP
Joined: 17 Jun 2008
Posts: 1502
Re: DS - Number Properties, Absolute Value [#permalink]

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29 Jan 2009, 03:09
mrsmarthi wrote:
My weak point in Quant is always DS and in specific it worst when they are related to Absolute values / Inequalities.

Can one of you please explain why my approach is wrong.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.

I know we can solve the DS questions by picking the numbers intelligently. But I am not able to rely on that process 100 %. So looking for alternate approaches on tackling DS questions.

What you are missing in the statement highlighted in red is that you are putting the left side in mod but not the right side. If I follow your steps then
|-x| = |y-z|
or, |x| = |y-z|

That is why stmt1 by itself is not sufficient.
Senior Manager
Joined: 30 Nov 2008
Posts: 482
Schools: Fuqua
Re: DS - Number Properties, Absolute Value [#permalink]

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29 Jan 2009, 15:38
scthakur wrote:
mrsmarthi wrote:
My weak point in Quant is always DS and in specific it worst when they are related to Absolute values / Inequalities.

Can one of you please explain why my approach is wrong.

Stmt 1 - X + Y = Z ==> X = Z - Y or -X = Y - Z ==> |X| = Y-Z. Sufficient.

Stmt 2 - X < 0 but no information related to Y & Z. Insufficient.

I know we can solve the DS questions by picking the numbers intelligently. But I am not able to rely on that process 100 %. So looking for alternate approaches on tackling DS questions.

What you are missing in the statement highlighted in red is that you are putting the left side in mod but not the right side. If I follow your steps then
|-x| = |y-z|
or, |x| = |y-z|

That is why stmt1 by itself is not sufficient.

yep true.....I missed that. Now I got it. Thank you.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: DS - Number Properties, Absolute Value   [#permalink] 29 Jan 2009, 15:38
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