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# If r, s are positive integers, is r/s a terminating decimal?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 7372
GMAT 1: 760 Q51 V42
GPA: 3.82
If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

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16 Mar 2018, 00:52
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Difficulty:

25% (medium)

Question Stats:

71% (00:52) correct 29% (00:59) wrong based on 46 sessions

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[GMAT math practice question]

If $$r, s$$ are positive integers, is $$\frac{r}{s}$$ a terminating decimal?

1) $$\frac{1}{r^2}$$ is a terminating decimal
2) $$\frac{1}{s^2}$$ is a terminating decimal

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MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Intern Joined: 04 Jan 2018 Posts: 2 Location: India Concentration: Marketing, Technology GMAT 1: 670 Q50 V30 GMAT 2: 710 Q50 V35 GPA: 3.74 WE: Consulting (Computer Software) Re: If r, s are positive integers, is r/s a terminating decimal? [#permalink] ### Show Tags 16 Mar 2018, 01:49 Is it B? Working: For 1/(x^2) to be a terminating decimal, x has to be either power or a multiple of (1,2,5). Stmt 1. Insufficient as terminating decimal depends on denominator. Stmt 2. Sufficient, as s is a multiple or power of (1,2,5) and whatever is value of r, r/s will be terminating decimal. Sent from my Lenovo P1a42 using GMAT Club Forum mobile app Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7372 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If r, s are positive integers, is r/s a terminating decimal? [#permalink] ### Show Tags 18 Mar 2018, 23:17 => 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. We can modify the question as follows: $$\frac{r}{s}$$ is a terminating decimal if and only if s has no other prime factors than $$2$$ and $$5$$. This is the same as condition 2). Condition 1) tells us nothing about the prime factors of s. Therefore, B is the answer. 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$149 for 3 month Online Course"
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Re: If r, s are positive integers, is r/s a terminating decimal?   [#permalink] 18 Mar 2018, 23:17
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