It is currently 18 Nov 2017, 13:12

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

a, b, s, k are different non-zero integers...

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

Hide Tags

Intern
Intern
avatar
B
Joined: 25 Jun 2017
Posts: 13

Kudos [?]: 1 [0], given: 0

a, b, s, k are different non-zero integers... [#permalink]

Show Tags

New post 02 Aug 2017, 16:28
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

67% (00:00) correct 33% (02:05) wrong based on 28 sessions

HideShow timer Statistics

a, b, k, s are different non-zero integers, \(\frac{2}{a}\) +\(\frac{4}{b}\) = \(\frac{k}{s}\) and \(\frac{k}{s}\) is maximally reduced. Does s = ab?

1) a and b are primes

2) a and b have gcd = 1

Sorry don't have the OA.

Kudos [?]: 1 [0], given: 0

Expert Post
Math Expert
User avatar
P
Joined: 02 Aug 2009
Posts: 5201

Kudos [?]: 5826 [0], given: 117

Re: a, b, s, k are different non-zero integers... [#permalink]

Show Tags

New post 03 Aug 2017, 09:21
Limara1 wrote:
a, b, k, s are different non-zero integers, \(\frac{2}{a}\) +\(\frac{4}{b}\) = \(\frac{k}{s}\) and \(\frac{k}{s}\) is maximally reduced. Does s = ab?

1) a and b are primes

2) a and b have gcd = 1

Sorry don't have the OA.



Hi...

It's all about what values can a and b take....

\(\frac{2}{a}\) +\(\frac{4}{b}\) = \(\frac{k}{s}\)...
\(\frac{2b+4a}{ab}=\frac{k}{s}\)..
I tells us a and b are prime..
If any of a or b is 2, it will cancel out from NUMERATOR, so k =ab/2... No
If they are prime other than 2, k=ab. Yes..
Different answers
Insufficient..
SAME will stand for II, where they are coprimes.
Ans E
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5826 [0], given: 117

Intern
Intern
avatar
B
Joined: 25 Jun 2017
Posts: 13

Kudos [?]: 1 [0], given: 0

a, b, s, k are different non-zero integers... [#permalink]

Show Tags

New post 03 Aug 2017, 11:24
chetan2u wrote:
Limara1 wrote:
a, b, k, s are different non-zero integers, \(\frac{2}{a}\) +\(\frac{4}{b}\) = \(\frac{k}{s}\) and \(\frac{k}{s}\) is maximally reduced. Does s = ab?

1) a and b are primes

2) a and b have gcd = 1

Sorry don't have the OA.



Hi...

It's all about what values can a and b take....

\(\frac{2}{a}\) +\(\frac{4}{b}\) = \(\frac{k}{s}\)...
\(\frac{2b+4a}{ab}=\frac{k}{s}\)..
I tells us a and b are prime..
If any of a or b is 2, it will cancel out from NUMERATOR, so s =ab/2... No
If they are prime other than 2, s=ab. Yes..
Different answers
Insufficient..
SAME will stand for II, where they are coprimes.
Ans E


You say that if a and b are primes other than 2 then s=ab, but is this always true? Can you prove this (i.e. prove that neither of primes a or b is a factor in b+2a)?

Anyway, for the purposes of this DS question it's enough to show that primes a and b CAN also be such that s=ab (which is pretty obvious, e.g. take a=3, b=5).

Kudos [?]: 1 [0], given: 0

Manager
Manager
User avatar
B
Joined: 23 May 2017
Posts: 161

Kudos [?]: 54 [0], given: 7

Concentration: Finance, Accounting
WE: Programming (Energy and Utilities)
Re: a, b, s, k are different non-zero integers... [#permalink]

Show Tags

New post 03 Aug 2017, 11:54
\(\frac{2}{a}\) + \(\frac{4}{b}\) = \(\frac{k}{s}\)

\(\frac{2b + 4a}{ab}\) = \(\frac{k}{s}\)

given : {2b + 4a} is not divisible by ab or there is no common factor of {2b + 4a} and ab

I have a question here ; Isn't the even value of a or b is out of scope(already discarded) due to the given statement that \(\frac{k}{s}\) is maximally reduced.

In that case we can pick only odd primes from statement 1 which will give us answer yes to the given question
_________________

If you like the post, please award me Kudos!! It motivates me

Kudos [?]: 54 [0], given: 7

Intern
Intern
avatar
B
Joined: 25 Jun 2017
Posts: 13

Kudos [?]: 1 [0], given: 0

a, b, s, k are different non-zero integers... [#permalink]

Show Tags

New post 03 Aug 2017, 17:57
Leo8 wrote:

given : {2b + 4a} is not divisible by ab or there is no common factor of {2b + 4a} and ab



I think you're mistaken here. The prompt says \(\frac{s}{k}\) is maximally reduced, NOT that \(\frac{2}{a}\) + \(\frac{4}{b}\) = \(\frac{2b+4a}{ab}\) is maximally reduced too.

In fact, the whole point of the question is to prove / disprove whether the latter is always true in this situation.

Kudos [?]: 1 [0], given: 0

a, b, s, k are different non-zero integers...   [#permalink] 03 Aug 2017, 17:57
Display posts from previous: Sort by

a, b, s, k are different non-zero integers...

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


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.