Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 21:03

1

This post received KUDOS

siddhans wrote:

What is the value of |x|? (1) x = –|x| (2) \(x^2\) = 4

Sorry but i am having a hard time understanding whats going on here and have got more confused...

x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2.

These 2 above statements confused me a lot...

if x=-2 ; whats the reason for doing this step |x| = |-2|? and then -|x| =-2 ??

What is modulus OR ||?

If a variable is -ve, and we wrap it around with ||, it becomes +ve. If a variable is +ve, and we wrap it around with ||, it remains +ve. If a variable is 0, and we wrap it around with ||, it remains 0.

So, -2; Wrap it around; |-2|=2 +2; Wrap it around; |+2|=+2=2 0; Wrap it around; |0|=0

Statement 1: (1) x = –|x|

Let's say x=1; L.H.S.=x=1 R.H.S.=-|x|=-|1|=-1 We know; 1 <> -1, so the expression x=-|x| doesn't hold good for x=1; And it won't hold good for any +ve number.

Now, let's say x=-1; L.H.S.=x=-1 R.H.S.=-|x|=-|-1|=-1 We know; -1 = -1, so the expression x=-|x| does indeed hold good for x=-1; And it will hold good for any -ve number.

For x=-0.464654 OR x=-100000; this expression will hold good. Thus, we won't be able to find a conclusive value for x. Not Sufficient. _________________

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 00:15

My point was to tell you that statement 1 is insufficient. I just tried to highlight different values of x and their relations. Nothing else. _________________

Hit kudos if my post helps you. You may send me a PM if you have any doubts about my solution or GMAT problems in general.

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 00:18

siddhans wrote:

Searched for this multiple times before posting but couldnt find it...

What is the value of |x| ? (1) x = –|x| (2) \(x^2\) = 4

It is not mandatory to solve it algebraically. I have seen modulus question can be solved using PIN quite well.

Here, Say; x=0; |x|=0; -|x|=0; x=-|x|; So, x can be 0. x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=2; |x|=2; -|x|=-2; x<>-|x|; So, x can't be 2. We see that the modulus of a +ve number is always +ve. When we flip the sign of it we get a -ve. Thus, x can't be +ve because a +ve will not be equal to -ve.

x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2. x=-3; |x|=|-3|=3; -|x|=-3; So, x=-|x|; x can be 3. In fact x can be any -ve number.

----------------------------------------------------------------------------------------- What you do TODAY is important because you're exchanging a day of your life for it! -----------------------------------------------------------------------------------------

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 20:10

fluke wrote:

siddhans wrote:

Searched for this multiple times before posting but couldnt find it...

What is the value of |x| ? (1) x = –|x| (2) \(x^2\) = 4

It is not mandatory to solve it algebraically. I have seen modulus question can be solved using PIN quite well.

Here, Say; x=0; |x|=0; -|x|=0; x=-|x|; So, x can be 0. x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=2; |x|=2; -|x|=-2; x<>-|x|; So, x can't be 2. We see that the modulus of a +ve number is always +ve. When we flip the sign of it we get a -ve. Thus, x can't be +ve because a +ve will not be equal to -ve.

x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2. x=-3; |x|=|-3|=3; -|x|=-3; So, x=-|x|; x can be 3. In fact x can be any -ve number.

x <= 0 AND |x| >= 0 Not Sufficient.

2) x^2=4 x=+-2 So, |x|=|-2|=2 Or |x|=|+2|=2

Either way, |x|=2 Sufficient.

Ans: "B"

Sorry but i am having a hard time understanding whats going on here and have got more confused...

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 20:13

fluke wrote:

siddhans wrote:

Searched for this multiple times before posting but couldnt find it...

What is the value of |x| ? (1) x = –|x| (2) \(x^2\) = 4

It is not mandatory to solve it algebraically. I have seen modulus question can be solved using PIN quite well.

Here, Say; x=0; |x|=0; -|x|=0; x=-|x|; So, x can be 0. x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=2; |x|=2; -|x|=-2; x<>-|x|; So, x can't be 2. We see that the modulus of a +ve number is always +ve. When we flip the sign of it we get a -ve. Thus, x can't be +ve because a +ve will not be equal to -ve.

x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2. x=-3; |x|=|-3|=3; -|x|=-3; So, x=-|x|; x can be 3. In fact x can be any -ve number.

x <= 0 AND |x| >= 0 Not Sufficient.

2) x^2=4 x=+-2 So, |x|=|-2|=2 Or |x|=|+2|=2

Either way, |x|=2 Sufficient.

Ans: "B"

Sorry but i am having a hard time understanding whats going on here and have got more confused...

x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2.

These 2 above statements confused me a lot...

if x=-2 ; whats the reason for doing this step |x| = |-2|? and then -|x| =-2 ??

Re: What is the value of |x| ? [#permalink]
08 Oct 2011, 21:41

fluke wrote:

siddhans wrote:

What is the value of |x|? (1) x = –|x| (2) \(x^2\) = 4

Sorry but i am having a hard time understanding whats going on here and have got more confused...

x=1; |x|=1; -|x|=-1; x<>-|x|; So, x can't be 1. x=-2; |x|=|-2|=2; -|x|=-2; So, x=-|x|; x can be 2.

These 2 above statements confused me a lot...

if x=-2 ; whats the reason for doing this step |x| = |-2|? and then -|x| =-2 ??

What is modulus OR ||?

If a variable is -ve, and we wrap it around with ||, it becomes +ve. If a variable is +ve, and we wrap it around with ||, it remains +ve. If a variable is 0, and we wrap it around with ||, it remains 0.

So, -2; Wrap it around; |-2|=2 +2; Wrap it around; |+2|=+2=2 0; Wrap it around; |0|=0

Statement 1: (1) x = –|x|

Let's say x=1; L.H.S.=x=1 R.H.S.=-|x|=-|1|=-1 We know; 1 <> -1, so the expression x=-|x| doesn't hold good for x=1; And it won't hold good for any +ve number.

Now, let's say x=-1; L.H.S.=x=-1 R.H.S.=-|x|=-|-1|=-1 We know; -1 = -1, so the expression x=-|x| does indeed hold good for x=-1; And it will hold good for any -ve number.

For x=-0.464654 OR x=-100000; this expression will hold good. Thus, we won't be able to find a conclusive value for x. Not Sufficient.

Thats a great explnation!!!... I knew what modulus is but confused on the cases you had mentioned earlier... Do you know how can we do this algebrically too? Just curious to know

Re: What is the value of |x| ? [#permalink]
09 Oct 2011, 09:01

38 Secs to figure its B :D _________________

GMAT is an addiction and I am darn addicted

Preparation for final battel: GMAT PREP-1 750 Q50 V41 - Oct 16 2011 GMAT PREP-2 710 Q50 V36 - Oct 22 2011 ==> Scored 50 in Quant second time in a row MGMAT---- -1 560 Q28 V39 - Oct 29 2011 ==> Left Quant half done and continued with Verbal. Happy to see Q39

Type of Visa: You will be applying for a Non-Immigrant F-1 (Student) US Visa. Applying for a Visa: Create an account on: https://cgifederal.secure.force.com/?language=Englishcountry=India Complete...

I started running back in 2005. I finally conquered what seemed impossible. Not sure when I would be able to do full marathon, but this will do for now...