NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 05:21 It is currently 26 Apr 2024, 05:21
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

Is j-k > 1/j - 1/k ?

SORT BY:
Date
Kudos
Tags:
Poor Qualityx      
Find Similar Topics 
Show Tags
Hide Tags
User avatar
guerrero25
Manager
Manager
Joined: 10 Apr 2012
Posts: 244
Own Kudos [?]: 4419 [1]
Given Kudos: 325
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE:Project Management (Telecommunications)
Send PM
GMAT ToolKit User
Is j-k > 1/j - 1/k ? [#permalink] New post   Updated on: 13 Apr 2013, 12:00
1
Kudos
00:00
A
B
C
D
E

Difficulty:

85% (hard)

Question Stats:

35% (02:04) correct 65% (02:10) wrong based on 31 sessions
Hide Show timer Statistics
Is j-k > 1/j - 1/k ?

1. jk> -1

2. -1< k< j

can I prove it using algebra and not picking number ?

This Question is Locked Due to Poor Quality
Hi there,
The question you've reached has been archived due to not meeting our community quality standards. No more replies are possible here.
Looking for better-quality questions? Check out the 'Similar Questions' block below for a list of similar but high-quality questions.
Want to join other relevant Problem Solving discussions? Visit our Data Sufficiency (DS) Forum for the most recent and top-quality discussions.
Thank you for understanding, and happy exploring!
ShowHide Answer
Official Answer
E

Originally posted by guerrero25 on 13 Apr 2013, 11:37.
Last edited by guerrero25 on 13 Apr 2013, 12:00, edited 2 times in total.
User avatar
B
yezz
Retired Moderator
Joined: 05 Jul 2006
Posts: 849
Own Kudos [?]: 1562 [0]
Given Kudos: 49
Send PM
GMAT ToolKit User
Re: Is j-k > 1/j - 1/k ? [#permalink] New post   13 Apr 2013, 11:39
guerrero25 wrote:
Is 100 j-k > 1/j - 1/k ?

1. jk> -1

2. -1< k< j

can I prove it using algebra and not picking number ?


plz revisit question is it 100j-k or 100(j-k) or the 100 is not there to start with
User avatar
guerrero25
Manager
Manager
Joined: 10 Apr 2012
Posts: 244
Own Kudos [?]: 4419 [0]
Given Kudos: 325
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE:Project Management (Telecommunications)
Send PM
GMAT ToolKit User
Re: Is j-k > 1/j - 1/k ? [#permalink] New post   13 Apr 2013, 11:54
[/quote]

plz revisit question is it 100j-k or 100(j-k) or the 100 is not there to start with[/quote]

Edited . Sorry about the junk number .
User avatar
B
yezz
Retired Moderator
Joined: 05 Jul 2006
Posts: 849
Own Kudos [?]: 1562 [1]
Given Kudos: 49
Send PM
GMAT ToolKit User
Re: Is j-k > 1/j - 1/k ? [#permalink] New post   13 Apr 2013, 12:07
1
Kudos
guerrero25 wrote:
Is j-k > 1/j - 1/k ?

1. jk> -1

2. -1< k< j

can I prove it using algebra and not picking number ?


is j-k > k-j / jk i.e. (j-k) - [(k-j)/jk] > 0 , is [jk(j-k) - (k-j)]/jk > 0 , i.e is[ jk(j-k) + (j-k)]/jk > 0 , i.e. is [(J-K)(JK+1)\ JK > 0

from 1

-1<jk<0 JK not = 0

i.e jk is -ve fraction, now to evaluate the question we ve ( jk+1) +ve and jk -ve , and thus we need to know j, k individually to evaluate (j-k).... no enough info ... insuff

from 2

still same like above .......insuff

both .......insuff E
User avatar
Zarrolou
Director
Director
Joined: 02 Sep 2012
Status:Far, far away!
Posts: 859
Own Kudos [?]: 4891 [1]
Given Kudos: 219
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
Send PM
GMAT ToolKit User
Re: Is j-k > 1/j - 1/k ? [#permalink] New post   13 Apr 2013, 12:22
1
Kudos
guerrero25 wrote:
Is j-k > 1/j - 1/k ?

1. jk> -1

2. -1< k< j

can I prove it using algebra and not picking number ?


\(j-k > \frac{1}{j} - \frac{1}{k}\) equals \(\frac{jk(j-k)-(k-j)}{jk}>0\) don't divide by jk because it could be 0
this is true if N+ and D+ or N- and D-

1. jk> -1 D could be -ve or +ve, no info about N. Not sufficient
2. -1< k< j j-k>0 and k-j<0 Num= \(jk(+ve)-(-ve)\)
jk could be +ve or -ve , Not sufficient

1+2 The numerator is jk(j-k)-(k-j) and from 2 we know that j-k>0 and k-j<0 so Num= \(jk(+ve)-(-ve)=\) and the Den is jk> -1.
Pick jk>0: Num>0 [(+ve)(+ve)-(-ve)>0] Den>0 so the answer is YES
pick -1<jk<0: Den<0 and there are no douts here, but what about the N? is N=(-ve)(+ve)-(-ve) a negative number? it depends, we cannot say.
E
User avatar
B
mau5
Verbal Forum Moderator
Joined: 10 Oct 2012
Posts: 485
Own Kudos [?]: 3093 [1]
Given Kudos: 141
Send PM
Re: Is j-k > 1/j - 1/k ? [#permalink] New post   15 Apr 2013, 11:09
1
Kudos
guerrero25 wrote:
Is j-k > 1/j - 1/k ?

1. jk> -1

2. -1< k< j



Basically the question boils down to : Is (j-k)(1+jk)jk>0.

From F.S 1, we have (1+jk)>0. Thus, we have to answer whether (j-k)jk>0. Also for jk>-1, we could have both j,k>0; both j,k<0 or j,k of the opposite signs.Insufficient.

From F.S 2, we have (j-k)>0. Thus, we have to answer whether (1+jk)jk>0. This is possible only if jk>0 OR if jk<-1. Insufficient.

Taking both together, we know that both (1+jk) and (j-k) are positive. Thus, we have to answer whether jk>0. Just as above, Insufficient.

E.

This Question is Locked Due to Poor Quality
Hi there,
The question you've reached has been archived due to not meeting our community quality standards. No more replies are possible here.
Looking for better-quality questions? Check out the 'Similar Questions' block below for a list of similar but high-quality questions.
Want to join other relevant Problem Solving discussions? Visit our Data Sufficiency (DS) Forum for the most recent and top-quality discussions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: Is j-k > 1/j - 1/k ? [#permalink]
15 Apr 2013, 11:09
Moderator:
Bunuel
Math Expert
92929 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions