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# Is integer R positive?

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Manager
Joined: 29 Oct 2010
Posts: 92
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Kudos [?]: 7 [0], given: 10

Is integer R positive? [#permalink]  27 Dec 2010, 09:34
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Difficulty:

45% (medium)

Question Stats:

37% (01:37) correct 63% (00:25) wrong based on 50 sessions
Is integer R positive?

(1) R^3 = R
(2) |R| = R
[Reveal] Spoiler: OA

Last edited by Bunuel on 03 Jul 2013, 05:38, edited 1 time in total.
Edited the question and added the OA
Manager
Joined: 29 Oct 2010
Posts: 92
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Kudos [?]: 7 [0], given: 10

Re: DS question [#permalink]  27 Dec 2010, 09:41
I have not understood why the second option is incorrect
Math Expert
Joined: 02 Sep 2009
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Re: DS question [#permalink]  27 Dec 2010, 09:50
Expert's post
Fairness wrote:
Is integer R positive?

1. R^3=R
2. lRl=R

Is integer R positive?

(1) R^3=R --> $$r^3-r=0$$ --> $$r(r^2-1)=0$$ --> $$r(r-1)(r+1)=0$$ --> $$r=0$$, $$r=1$$, or $$r=-1$$. Not sufficient.

(2) |R|=R --> $$r$$ is some non-negative integer, so $$r$$ can be 0 or any positive integer. Not sufficient.

(1)+(2) $$r$$ can be 0, so not a positive integer or 1, a positive integer, two different answers, hence not sufficient.

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Manager
Joined: 29 Oct 2010
Posts: 92
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Kudos [?]: 7 [0], given: 10

Re: DS question [#permalink]  28 Dec 2010, 03:06
Thanks, I missed the word " integer"

Posted from my mobile device
Re: DS question   [#permalink] 28 Dec 2010, 03:06
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