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Director
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What is x? (1) x < 2 (2) x = 3x 2 [#permalink]
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20 Oct 2007, 21:50
What is x?
(1) x < 2
(2) x = 3x – 2 == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost 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.



Director
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Re: MGMAT Math Modulus [#permalink]
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20 Oct 2007, 22:09
eyunni wrote: What is x?
(1) x < 2
(2) x = 3x – 2
i get E
(1)
for x > 0 => x < 2
for x < 0 => x > 2
so range of x = 2 < x < 2
not sufficient
(2)
for x > 0 => x = 3x  2
2x = 2 : x = 1
for x < 0 => x = 3x  2
4x = 2 : x = 1/2
x could be 1 or 1/2, not sufficient
putting (1) and (2) together, both 1 and 1/2 fits in 2 < x < 2
so both not sufficient



Director
Joined: 03 May 2007
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Schools: University of Chicago, Wharton School

Re: MGMAT Math Modulus [#permalink]
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Updated on: 20 Oct 2007, 22:14
eyunni wrote: What is x?
(1) x < 2 (2) x = 3x – 2
E.
From 1, x could be anything smaller than 2 but grater than 2. nsf
From 2, x = 1/2 and 1. nsf
from 1 and 2 also nsf.
Originally posted by Fistail on 20 Oct 2007, 22:11.
Last edited by Fistail on 20 Oct 2007, 22:14, edited 3 times in total.



VP
Joined: 28 Mar 2006
Posts: 1329

Fistail wrote: trivikram wrote: yes it should be B how???
Mistake....I messed a calculation here..
squaring both sides in (B) and applyingA would lead us to E



SVP
Joined: 01 May 2006
Posts: 1786

Perfect explanation from beckee529 .... Nothing to add



Manager
Joined: 07 Mar 2007
Posts: 189

Statement 1 is an absolute so we have 2 possibilities. When X is positive and when X is negative.
So, x < 2
1. x<2 or
x<2>2
So, when x > 0 => x < 2
And if x <0> x > 2



Manager
Joined: 27 Jul 2007
Posts: 103

ColumbiaDream wrote: Statement 1 is an absolute so we have 2 possibilities. When X is positive and when X is negative.
So, x < 2 1. x<2 or x<2>2
So, when x > 0 => x < 2 And if x <0> x > 2
But from stmt 2
for x > 0 => x = 3x  2
2x = 2 : x = 1
for x <0> x = 3x  2
4x = 2 : x = 1/2
here with x<0 we r gettin x=1/2 ????



Manager
Joined: 27 Jul 2007
Posts: 103

ColumbiaDream wrote: Statement 1 is an absolute so we have 2 possibilities. When X is positive and when X is negative.
So, x < 2 1. x<2 or x<2>2
So, when x > 0 => x < 2 And if x <0> x > 2
But from stmt 2
for x > 0 => x = 3x  2
2x = 2 : x = 1
for x <0> x = 3x  2
4x = 2 : x = 1/2
here with x<0 we r gettin x=1/2 ????



Manager
Joined: 07 Mar 2007
Posts: 189

Yes you're right.
Because when you take the absolute into consideration, the equations is:
x=3x2 > 4x=2> x=1/2



Manager
Joined: 07 Mar 2007
Posts: 189

But How can B alone be sufficient? We get two values  x=1 or x=1/2
Eyunni could you please share the source of this question?



Manager
Joined: 18 Jun 2007
Posts: 55

The question probably assumed X was an integer.



Manager
Joined: 07 Mar 2007
Posts: 189

But in DS how can we ASSUME x is an integer? I thought we had to be told if this was the case. Am i wrong?



SVP
Joined: 01 May 2006
Posts: 1786

(B) it is ... I didnt look in all details of the explanations given precedently...
What is x?
(1) x < 2
(2) x = 3x – 2
Stat1
x < 2
<=> 2 < x < 2
INSUFF.
Stat1
x = 3x – 2
o If x >= 0, then
x = 3x – 2
<=> x = 3x  2
<=> x = 1 >>>> Solution ok as 1 > 0 (x>=0)
o If x < 0, then
x = 3x – 2
<=> x = 3x  2
<=> x = 1/2 >>>> Solution out as x must be negative 0
So, we have unique solution for x : 1
SUFF.



SVP
Joined: 01 May 2006
Posts: 1786

ColumbiaDream wrote: But in DS how can we ASSUME x is an integer? I thought we had to be told if this was the case. Am i wrong?
Actually u are right. If not stated, we can never assume that a variable is an integer.
Here, it's just because x = 1/2 is ruled out as x < 0.



Director
Joined: 11 Jun 2007
Posts: 595

ColumbiaDream wrote: But How can B alone be sufficient? We get two values  x=1 or x=1/2
Eyunni could you please share the source of this question?
That was a touch tricky. I don't remember the source exactly but I guess it is from MGMAT/ Kaplan.



Manager
Joined: 28 Apr 2008
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Re: MGMAT Math Modulus [#permalink]
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25 Nov 2008, 12:15
B
1> 2<x<2 insuff
2> x=3x2, x>0 x=23x, x<0
for x<0, 23x is allways +ve> thus x>0
sufficient



VP
Joined: 05 Jul 2008
Posts: 1333

Fig wrote: (B) it is ... I didnt look in all details of the explanations given precedently... What is x? (1) x 2 = 0, then[/b] x = 3x – 2 x = 3x  2 x = 1 >>>> Solution ok as 1 > 0 (x>=0) [b]o If x x = 3x  2 x = 1/2 >>>> Solution out as x must be negative 0 So, we have unique solution for x : 1 SUFF. Whew! What the Q did is lot of trickery. Lets us start with x 0 and then rule out that case as it leads to a contradiction. == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost 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.










