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# If b≠0, and |ab|=ab, is b>0?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 8023
GMAT 1: 760 Q51 V42
GPA: 3.82
If b≠0, and |ab|=ab, is b>0?  [#permalink]

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22 Mar 2018, 00:52
00:00

Difficulty:

35% (medium)

Question Stats:

67% (01:25) correct 33% (01:21) wrong based on 106 sessions

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[GMAT math practice question]

If $$b≠0$$, and $$|ab|=ab,$$ is $$b>0$$?

$$1) a<0$$
$$2) \frac{a}{b}>0$$

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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 $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Current Student Joined: 07 Jan 2016 Posts: 1086 Location: India GMAT 1: 710 Q49 V36 Re: If b≠0, and |ab|=ab, is b>0? [#permalink] ### Show Tags 22 Mar 2018, 01:46 MathRevolution wrote: [GMAT math practice question] If $$b≠0$$, and $$|ab|=ab,$$ is $$b>0$$? $$1) a<0$$ $$2) \frac{a}{b}>0$$ mod ab always has a positive value hence ab = positive a and b can both be negative or a and b can both be positive 1) a is negative sufficient to answer 2) a/b > 0 here again both a and b can positive/negative - insufficient a clear A Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8023 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If b≠0, and |ab|=ab, is b>0? [#permalink] ### Show Tags 25 Mar 2018, 18:18 => Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution. The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question. $$|ab| = ab$$ $$=> ab ≥ 0$$ Condition 1) Since $$a < 0, b≠0$$ and $$ab ≥ 0$$, we have $$b < 0$$. Thus, the answer is ‘no’. Since ‘no’ is also a unique answer by CMT (Common Mistake Type) 1, condition 1) is sufficient. Condition 2) If $$a = 1$$ and $$b = 1$$, the answer is ‘yes’. If $$a = -1$$ and $$b = -1$$, the answer is ‘no’. Since we don’t have a unique solution, condition 2) is not sufficient. Therefore, A is the answer. Answer: A _________________ 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$79 for 1 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Re: If b≠0, and |ab|=ab, is b>0?   [#permalink] 25 Mar 2018, 18:18
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