GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 24 Apr 2019, 21:41

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

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

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 7245
GMAT 1: 760 Q51 V42
GPA: 3.82
If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post 04 Feb 2016, 18:25
1
2
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

76% (00:47) correct 24% (01:10) wrong based on 145 sessions

HideShow timer Statistics

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

1) 1/r is a terminating decimal
2) 1/s is a terminating decimal


* A solution will be posted in two days.

_________________
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"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7588
Re: If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post 04 Feb 2016, 19:15
MathRevolution wrote:
If r, s are positive integers, is r/s a terminating decimal?

1) 1/r is a terminating decimal
2) 1/s is a terminating decimal


* A solution will be posted in two days.


Hi all,
whether r/s is a terminating decimal will depend on value of s, if r/s is in its simplified form..
1) 1/r is a terminating decimal
nothing about s.. insuff

2) 1/s is a terminating decimal
if 1/s is a terminating decimal..
when it is multiplied with r, it can be an integer or a terminating decimal..
so suff

ans B
_________________
CEO
CEO
User avatar
D
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2908
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
Reviews Badge
Re: If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post 05 Feb 2016, 07:03
MathRevolution wrote:
If r, s are positive integers, is r/s a terminating decimal?

1) 1/r is a terminating decimal
2) 1/s is a terminating decimal


* A solution will be posted in two days.


Question : is r/s a terminating decimal?

r/s will be a terminating decimal if in least form the fraction r/s has denominator made up of no prime factors other than 2 and/or 5

Statement 1: 1/r is a terminating decimal
i.e. r contains no prime factor other than 2 and 5. But since we are seeking information primarily about denominator of fraction r/s therefore
NOT SUFFICIENT

Statement 2: 1/s is a terminating decimal
i.e. s contains no prime factor other than 2 and 5 which is exactly what we were looking for therefore
SUFFICIENT

Answer: Option B
_________________
Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION
Intern
Intern
User avatar
Joined: 07 Oct 2014
Posts: 9
If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post Updated on: 08 Feb 2016, 14:12
MathRevolution wrote:
If r, s are positive integers, is r/s a terminating decimal?

1) 1/r is a terminating decimal
2) 1/s is a terminating decimal


* A solution will be posted in two days.

Decimal is terminating when it can be expressed as \(\frac{K}{2^n5^m}\), where n, m are non-negative integers and k is an integer (e. g. 0.1 can be expressed as \(\frac{1}{2^15^1}\); 0.015 can be expressed as \(\frac{15}{2^35^3}\) or \(\frac{3}{2^35^2}\) etc)

1) \(\frac{1}{r}\) is a terminating decimal, thus, can be expressed as \(\frac{1}{2^n5^m}\), \(r=2^n5^m\).
If s=5, then \(\frac{r}{s}=\frac{2^n5^m}{5}\), terminating.
If s=3, then \(\frac{r}{s}=\frac{2^n5^m}{3}\), not terminating.
Insufficient.

2) \(s=2^n5^m\)
\(\frac{r}{s}=\frac{r}{2^n5^m}\). Since r, s are positive integers, then the expression is a terminating decimal for any r,s.

Sufficient.

B

Originally posted by soloveva on 05 Feb 2016, 10:31.
Last edited by soloveva on 08 Feb 2016, 14:12, edited 2 times in total.
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 7245
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post 08 Feb 2016, 00:11
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

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

1) 1/r is a terminating decimal
2) 1/s is a terminating decimal


When you modify the original condition and the question, a terminating decimal is a fraction that only 2 and 5 are the prime factors of a denominator. So, you only need to figure out s from r/s.
Therefore, the answer is B.


 Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
_________________
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"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 10625
Re: If r, s are positive integers, is r/s a terminating decimal?  [#permalink]

Show Tags

New post 18 Aug 2017, 15:07
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: If r, s are positive integers, is r/s a terminating decimal?   [#permalink] 18 Aug 2017, 15:07
Display posts from previous: Sort by

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

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.