Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 11 Feb 2011
Posts: 134

what is x? A.x<2 B.x=3x2 [#permalink]
Show Tags
16 Jun 2011, 08:06
Question Stats:
41% (01:37) correct
59% (00:35) wrong based on 50 sessions
HideShow timer Statistics
what is x? A.x<2 B.x=3x2
_________________
target:810 out of 800!



Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2010

Re: inequality! [#permalink]
Show Tags
16 Jun 2011, 09:32
AnkitK wrote: what is x? A.x<2 B.x=3x2 Sol: Q: What is x? 1. 2<x<2 Not Sufficient. 2. x=3x2 2x=2 x=1 OR x=3x2 4x=2 x=1/2 Not Sufficient. Combining both; 1/2 and 1 both lie between 2<x<2 Not Sufficient. Ans: "E"
_________________
~fluke
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 11 Feb 2011
Posts: 134

Re: inequality! [#permalink]
Show Tags
16 Jun 2011, 09:34
Yeah i did the same but to my sorrow OA is B .
_________________
target:810 out of 800!



Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2010

Re: inequality! [#permalink]
Show Tags
16 Jun 2011, 09:40
AnkitK wrote: Yeah i did the same but to my sorrow OA is B . B would be the answer if it is mentioned that x is an integer.
_________________
~fluke
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 11 Feb 2011
Posts: 134

Re: inequality! [#permalink]
Show Tags
16 Jun 2011, 09:43
No not mentioned anywhere.Anyways thnkx for your response.
_________________
target:810 out of 800!



Intern
Joined: 18 May 2011
Posts: 7

Re: inequality! [#permalink]
Show Tags
19 Jun 2011, 04:28
Because x = 1/2 doesn’t satisfy the second condition which is IxI= 3x2. Therefore we are left with only one value, x=1.



Manager
Joined: 14 Feb 2010
Posts: 160
Location: Banaglore

Re: inequality! [#permalink]
Show Tags
05 Jul 2011, 06:41
AnkitK wrote: what is x? A.x<2 B.x=3x2 A : insufficient B : taking two scenarios when x< 0 and when x > 0 when x< 0 : x=3x2 > x = 1/2 , this is not a valid solution since we assumed x<0 therefore the soulution is invalid.when x>0 then x=3x2 > x = 1 , this is a valid solution since we assumed that x > 0 , therefore Conditon B gives us a unique answer i.e. x= 1. Hence the answer is B.



Manager
Joined: 18 Oct 2010
Posts: 90

Re: inequality! [#permalink]
Show Tags
05 Jul 2011, 10:48
AnkitK wrote: Yeah i did the same but to my sorrow OA is B . i dont think that we need a condition " x must be an integer to get the answer B because statement 1 is surely not sufficient. statement 2 could be case first: if x> 0 so x is 1 case secondL if x< so so x is 1/2 . this case should be eliminated becos x must be negative so if x=1/2 this case will be deleted.... thus x=1



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7438
Location: Pune, India

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 03:18
AnkitK wrote: what is x? A.x<2 B.x=3x2 You are missing an important point  let me explain. We all know that if we have mods, we take two cases  positive and negative  and then solve the equation. The point is  why do we do that? If you remember, this is how we define mods x = x if x is positive and x if x is negative So basically, x takes different forms depending on whether x is positive or negative. When I want to solve x=3x2, I can't solve with x. So I split it into two cases: Case 1: x is positive I get x = 3x  2 x = 1 I accept this value of x since x has to be +ve and satisfy given equation. It does both. Case 2: x is negative x = 3x  2 x = 1/2 I reject this value since x should be negative for the equation to look like this. So x can only take 1 value i.e. x = 1. Remember, when you split x into two cases, you have to check that the value you get lies in the region in which you are expecting it to lie.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Senior Manager
Joined: 03 Mar 2010
Posts: 440

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 03:53
Good explanation VeritasPrepKarishma!
_________________
My dad once said to me: Son, nothing succeeds like success.



Intern
Joined: 29 Jun 2011
Posts: 16

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 05:05
I think there is a flaw in above explanations
in case if x is negative then we cannot say x=3x2 we should say x= 3x 2 2x=2 so x= 1



Manager
Joined: 03 Jun 2010
Posts: 137
Location: Dubai, UAE
Schools: IE Business School, Manchester Business School, HEC Paris, Rotterdam School of Management, Babson College

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 05:50
Answer is E Statement 1 is insufficient x<2 x>2 x<2 insufficient Statement 2 insufficient x=3x2 X=1, 1/2 Both taken together No single concise value as that is required for DS problems with value questions. Posted from GMAT ToolKit



Current Student
Joined: 26 May 2005
Posts: 563

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 06:03
AnkitK wrote: what is x? A.x<2 B.x=3x2 St 1: X lies between 2 and 2 .. not sufficient St2: X>0 X= 3x2 2x= 2 X =1 .. check if it satifies the equation 1 = 3(1)2 = 1 ... satisfies X<0 x = 3x2 4x = 2 x= 1/2 again check if satisfies the equation 1/2 = 3(1/2) 2 = 1/2 ... doesnt satisfy the equation Hence X =1 Answer has to B . I dont think that the question requires to say that X is an integer. only trick/tip here is : whenever there is Mod or Inequality , check the value whether it satifies the equation.



Manager
Joined: 16 Jan 2011
Posts: 103

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 10:47
"I reject this value since x should be negative for the equation to look like this. So x can only take 1 value i.e. x = 1."
im sorry but could you please explaine why you reject 1/2... its also positive as 1



Manager
Joined: 07 Oct 2010
Posts: 176

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 11:33
I dont know why is this question extended so much
Option A id definitely insufficient
Now in option B people are confused whether 1/2 can be a value of the x or not But people ....try putting x=1/2 in the option B equation .... l x l = 3x2 therefore l 1/2 l = 3*1/2 2 here l 1/2 l will be +ve ...i.e. 1/2 therefore 1/2 = 3/2  2 = (34)/2 hence 1/2 =  1/2 ...which is not possible
similarly we even take x as 1/2 then also the resulting values come as 1/2 =  7/2 ...again unequal ....
Hence x can take only one value and that is 1
Hence ans has to be B



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7438
Location: Pune, India

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 21:07
getmydream wrote: I think there is a flaw in above explanations
in case if x is negative then we cannot say x=3x2 we should say x= 3x 2 2x=2 so x= 1 In case x is negative, 3x does not change to 3x. When we write 'x', the negative sign is already included. But when x is negative, x becomes x. The reason is that x can never be negative. If x is negative, x makes it positive. e.g. If x = 4 x = 4 = 4 which is actually x = (4) = 4 Hence x = x when x is negative. When x is positive, x = x
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7438
Location: Pune, India

Re: inequality! [#permalink]
Show Tags
06 Jul 2011, 21:16
Galiya wrote: "I reject this value since x should be negative for the equation to look like this. So x can only take 1 value i.e. x = 1."
im sorry but could you please explaine why you reject 1/2... its also positive as 1 Let me highlight the main points: x = x if x is positive and [highlight]x = x if x is negative[/highlight] (As explained in the reply above) Case 1: x is positive x=3x2 becomes x=3x2 When I solve this, I get x = 1. This is acceptable since here I am working on the case where x is positive. [highlight]Case 2: x is negative[/highlight] [highlight]x[/highlight]=3x2 becomes [highlight]x[/highlight]= 3x  2 Now I solve and get a value of x. This value will be acceptable only if it is negative since I am working on the case where x is negative. But when I solve, I get x = 1/2. It is not negative so I reject it. To test, try and put x = 1 in x=3x2 It satisfies. Put x = 1/2 in x=3x2 It doesn't satisfy.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Manager
Joined: 27 Dec 2007
Posts: 74

Re: inequality! [#permalink]
Show Tags
07 Jul 2011, 04:24
Thanks Karishma for the explanation >



Manager
Status: ==GMAT Ninja==
Joined: 08 Jan 2011
Posts: 242
Schools: ISB, IIMA ,SP Jain , XLRI
WE 1: Aditya Birla Group (sales)
WE 2: Saint Gobain Group (sales)

Re: inequality! [#permalink]
Show Tags
08 Jul 2011, 10:37
AnkitK wrote: what is x? A.x<2 B.x=3x2 B for me (X>0 And x=1)
_________________
WarLocK _____________________________________________________________________________ The War is oNNNNNNNNNNNNN for 720+ see my Test exp here http://gmatclub.com/forum/mytestexperience111610.html do not hesitate me giving kudos if you like my post.



Director
Joined: 01 Feb 2011
Posts: 755

Re: inequality! [#permalink]
Show Tags
08 Jul 2011, 20:31
1. Not sufficient 2<x<2
2. Sufficient
when x>=0, x =3x2 => x =1 when x<0 , x=3x2 => x =1/2 , but this is not valid as x<0.
so x can only be 1.
Answer is B.







Go to page
1 2
Next
[ 21 posts ]




