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# r=?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6407
GMAT 1: 760 Q51 V42
GPA: 3.82

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23 May 2017, 02:25
00:00

Difficulty:

35% (medium)

Question Stats:

63% (00:45) correct 38% (00:51) wrong based on 42 sessions

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r=?

1) $$r^3-r^2=0$$
2) $$r=-r$$

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MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Senior Manager Joined: 06 Jan 2015 Posts: 489 Location: India Concentration: Operations, Finance GPA: 3.35 WE: Information Technology (Computer Software) Re: r=? [#permalink] ### Show Tags 23 May 2017, 03:24 MathRevolution wrote: r=? 1) $$r^3-r^2=0$$ 2) $$r=-r$$ 1) $$r^3-r^2=0$$=$$r^2(r-1)=0$$ r=0 or 1 2) $$r=-r$$ => 2r=0 i,e r=0 Hence B _________________ आत्मनॊ मोक्षार्थम् जगद्धिताय च Resource: GMATPrep RCs With Solution Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6407 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: r=? [#permalink] ### Show Tags 25 May 2017, 01:16 ==> In the original condition, there is 1 variable (r), and in order to match the number of variables to the number of equations, there must be 1 equation. Since there is 1 for con 1) and 1 for con 2), D is most likely to be the answer. For con 1), from r2(r-1)=0, you get r=0,1, hence it is not unique and not sufficient. For con 2), from 2r=0, you get r=0, hence it is unique and sufficient. Therefore, the answer is B. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Re: r=? &nbs [#permalink] 25 May 2017, 01:16
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