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# Find C + |C|

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Manager
Joined: 17 Mar 2010
Posts: 155
Find C + |C|  [#permalink]

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17 Sep 2010, 05:51
15
00:00

Difficulty:

55% (hard)

Question Stats:

53% (00:51) correct 47% (00:45) wrong based on 380 sessions

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Find C + |C|

(1) |C|=1
(2) $$C^2= \sqrt{C}$$
Retired Moderator
Joined: 02 Sep 2010
Posts: 774
Location: London
Re: Find C + |C|  [#permalink]

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17 Sep 2010, 05:54
1
amitjash wrote:
Find C+|C|
1. |C|=1
2. C^2= Sqrt C

(1) |C|=1 means C is 1 or -1. Not sufficient

(2) C^2 = sqrt(C) means either C=0 or C=1. not sufficient

(1)+(2) => C=1. Sufficient

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Schools: ISB, HEC, Said
Re: Find C + |C|  [#permalink]

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21 Sep 2010, 06:16
1
I think the point here people likely to mis is C can be zero. As it happened in my case.
These mistakes can be very costly in GMAT.
Nice question thanks for posting
Director
Joined: 07 Jun 2004
Posts: 604
Location: PA
Re: Find C + |C|  [#permalink]

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21 Sep 2010, 08:30
I went with this explnation

S1 c can be -1 or 1 not sufficent

S2 c ^2 = sqrt( c) square both sides C ^ 4 = c or c ( c^3 - 1 ) = 0

c = 0 or c = 1 not sufficient

S1 and S2 we can say c = 1
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Joined: 20 Jul 2010
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Re: Find C + |C|  [#permalink]

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21 Sep 2010, 10:57
prashantbacchewar wrote:
I think the point here people likely to mis is C can be zero. As it happened in my case.
These mistakes can be very costly in GMAT.
Nice question thanks for posting

I missed 0 too......ha silly me......
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Re: Find C + |C|  [#permalink]

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01 Mar 2015, 15:29
Hi All,

The others posters in this thread have properly solved the problem, so I won't rehash any of that work here. Instead, I want to point out some details on the "nature" of DS questions. DS questions are on the GMAT to test you on a variety of skills that are not strictly "math skills": organization, accuracy, attention-to-detail, thoroughness, the ability to PROVE that you're correct, etc.

Every DS question has AT LEAST one answer. Part of your job when facing any DS question is to look "beyond" the obvious. To get the points, you have to show how thorough your thinking is by finding the alternatives (if they exist).

In Fact 2, I'm sure that almost everyone would think "oh, it has to be the number 1...."; if those same Test Takers don't do the necessary extra work to realize that 0 is ALSO a possible answer, then those same people will get this easy question wrong, lose out on those points and not even know it. Get in the habit of thinking - do work, take notes, consider the possibilities and you'd be amazed how easy most DS questions actually are.

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Rich
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Re: Find C + |C|  [#permalink]

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01 Aug 2018, 17:48
I made a silly mistake and forgot that the square root of a negative number is i haha.

Nice post!
Re: Find C + |C| &nbs [#permalink] 01 Aug 2018, 17:48
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# Find C + |C|

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