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Senior Manager
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For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
 28 Feb 2013, 14:04
Question Stats:
83% (01:22) correct
16% (00:45) wrong based on 14 sessions
For what value of x, is |x – 3| + |x + 1| + |x| = 10? (A) 0 (B) 3 (C) -3 (D) 4 (E) -2
Last edited by mun23 on 28 Feb 2013, 14:28, edited 3 times in total.
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Manager
Status: Helping People Ace the GMAT
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 14:11
I think you meant for the answer to be D.... |4 - 3| + |4 + 1| + |4| |1| + |5| + |4| = 10
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Senior Manager
Status: struggling with GMAT
Joined: 06 Dec 2012
Posts: 323
Location: Bangladesh
Concentration: Accounting
GMAT Date: 04-06-2013
GPA: 3.65
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27
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‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ [#permalink]
28 Feb 2013, 14:13
‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ The answer is 0. Why?
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 14:31
Answer cannot be C. The above equation only works with option D i.e. x=4.
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Manager
Status: Helping People Ace the GMAT
Affiliations: GMAT Prepster and Stratus Prep
Joined: 16 Jan 2013
Posts: 142
Location: United States
Concentration: Finance, Entrepreneurship
GMAT 1: 770 Q50 V46
GPA: 3.1
WE: Consulting (Consulting)
Followers: 5
Kudos [?]:
36
[0], given: 4
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Re: ‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ [#permalink]
28 Feb 2013, 14:52
mun23 wrote: ‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ The answer is 0. Why? This should define x as and integer. I would be careful with your sources...
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Jim Kernan is the Director of GMAT Operations at Stratus Prep and author of GMAT Materials for GMAT Prepster.
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Veritas Prep GMAT Instructor
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 15:34
mun23 wrote: For what value of x, is |x – 3| + |x + 1| + |x| = 10?
(A) 0
(B) 3
(C) -3
(D) 4
(E) -2 Often on these types of questions you're better off just plugging in answer choices and seeing which one is correct. Once you plug in 3 and get (3-3) + (3+1) + 3 = 7, you can figure out that if you added one more to X, you'd get a new answer that's 3 higher than your old answer. However, even if you don't overthink anything and just plug the choices in in succession, you still get the right answer in well under 2 minutes. If you're struggling with these types of questions, keep it simple and you'll be fine. Hope this helps! -Ron
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 20:06
VeritasPrepRon wrote: mun23 wrote: For what value of x, is |x – 3| + |x + 1| + |x| = 10?
(A) 0
(B) 3
(C) -3
(D) 4
(E) -2 Often on these types of questions you're better off just plugging in answer choices and seeing which one is correct. Once you plug in 3 and get (3-3) + (3+1) + 3 = 7, you can figure out that if you added one more to X, you'd get a new answer that's 3 higher than your old answer. However, even if you don't overthink anything and just plug the choices in in succession, you still get the right answer in well under 2 minutes. If you're struggling with these types of questions, keep it simple and you'll be fine. Hope this helps! -Ron Here you can: a) test each answer choice OR b) take the algebra way Both are fast but it depends how you are comfortable but if you start thinking about the positive side of absolute value ---> x - 3 + x + 1 + x = 10 ---> 3x = 12 x = 4 OR- x + 3 -x - 1 - x = 10 ----> - 3x = 8 NOT POSSIBLE Only D takes in account. in no more than 50 seconds - 60 at maximum regards
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 21:01
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carcass wrote:
Here you can:
a) test each answer choice OR
b) take the algebra way
Both are fast but it depends how you are comfortable but if you start thinking about the positive side of absolute value ---> x - 3 + x + 1 + x = 10 ---> 3x = 12 x = 4 OR- x + 3 -x - 1 - x = 10 ----> - 3x = 8 NOT POSSIBLE
Only D takes in account. in no more than 50 seconds - 60 at maximum
regards
Going the algebra way, you have missed two cases. There are 3 transition points: -1, 0, 3 When x > 3, |x - 3| + |x + 1| + |x| = 10x - 3 + x + 1 + x = 10x = 4 Satisfies When 0 < x < 3 |x - 3| + |x + 1| + |x| = 10-(x - 3) + (x + 1) + x = 10x = 6 (Not possible since 0 < x < 3) When -1 < x < 0 |x - 3| + |x + 1| + |x| = 10-(x - 3) + -(x + 1) + x = 10x = -8 (Not possible since -1 < x < 0) When x < -1 |x - 3| + |x + 1| + |x| = 10-(x - 3) - (x+1) - x = 10 x = -8/3 Satisfies Better is the number line method I discussed in this post: http://www.veritasprep.com/blog/2011/01 ... s-part-ii/The question has been picked from here. Mind you, I have discussed two different questions: 1. For what value of x, is |x – 3| + |x + 1| + |x| = 10? 2. For how many values of x, is |x – 3| + |x + 1| + |x| = 10? The method to be used is different in the two cases. As Ron mentioned above, just plug in the options in the first question. In the second question, you can use the number line to quickly solve it. Check out the post to avoid confusion.
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Re: ‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ [#permalink]
28 Feb 2013, 21:06
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JimGMATPrepster wrote: mun23 wrote: ‘For how many values of x, is |x – 3| + 3|x + 1| + |x| = 4?’ The answer is 0. Why? This should define x as and integer. I would be careful with your sources... There is no reason to define x as an integer. There is no value of x which satisfies this equation - integer or real number.
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Veritas Prep GMAT Instructor
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
28 Feb 2013, 21:08
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There are various different questions in this post which is creating confusion. To get the correct answer of each one of them, kindly check my post and the responses below it: http://www.veritasprep.com/blog/2011/01 ... s-part-ii/
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
01 Mar 2013, 03:26
Thanks Mod  to point out a detailed explanatio. I know that for each absolute value you have to considere a sign positive and negative. However, as soon as possible you realize that on two value there is 4 (among the answers) and -8/3 is almost impossible to have another solution for two reasons: 1) we are in gmat land and each question is constructed in a certain way. (but of course) 2) is a intuitive method: doing a lot of practice then you know how the things work because is always the same thing, actually. I mean: it's like in CR: I always read the stimulus and after the question stem but often when I finish the stimulus I know from the tone of the question, from how the same unfold and so on what will be the question: weaken and so on......a do not read the stem at all, simply because for the logic of the question, the same must go in one direction instead of another. Anyway, Thanks . It's always useful to repeat over and over again the concepts (and I'm a huge fan of you).
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Senior Manager
Status: struggling with GMAT
Joined: 06 Dec 2012
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Location: Bangladesh
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GMAT Date: 04-06-2013
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
01 Mar 2013, 08:25
Hi karisma
Whats the difference between for what value of x &for how many values of x.........
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
01 Mar 2013, 18:34
I think this question is not hard for us to explain: when x >3, when 0 < x < 3, .... If we write exam, we don't have much time to do like this.
I think we should use the answers into equation, we have the answer faster than divide into some parts (x > 3, 0 < x < 3)
Answer is 4
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10? [#permalink]
01 Mar 2013, 22:29
mun23 wrote: Hi karisma
Whats the difference between for what value of x &for how many values of x......... 'For what value of x....' implies you are looking for one particular value of x. There could be 2 or more values satisfying this equation but you are looking for only one - the one which is included in your options. x can take two values here: 4 and -8/3 'For what value of x....' will be answered by 4. 4 is one of the values that satisfy this equation. The other one, -8/3, is not in the options which is logical since only one option can be correct. This question is generally simpler since you can plug in the options to see which value satisfies the equation. 'For how many values of x ...' means 'how many values can x take?' The answer here will be 2. x can take 2 values: 4 and -8/3. This question is usually more complex. You need to find the number of values x can take. The options will be something like: 0, 1, 2, 3, 'More than 3'. Here, you cannot plug in the options since the options do not give you the values x can take. They only give you the number of values. So you actually need to solve the equation to get how many values x can take.
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Re: For what value of x, is |x – 3| + |x + 1| + |x| = 10?
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01 Mar 2013, 22:29
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