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.
It appears that you are browsing the GMAT Club forum unregistered!
Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club
Registration gives you:
Tests
Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.
Applicant Stats
View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more
Books/Downloads
Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!
Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
27 Feb 2013, 21:22
Expert's post
mun23 wrote:
If a is not equal to b, is 1/(a-b) > ab ?
(1) |a| > |b| (2) a < b
From F.S 1, let's assume a = -3 and b = -2. Thus, 1/(a-b) = -1 and a*b = 6. Thus, as -1<6, the answer to the question stem is No. Again, pick a = -3 and b = 2, and 1/(a-b) = -0.2, and a*b = -6. In this case we see that -0.2>-6, thus the answer to the question stem is a YES. Insufficient.
From F.S 2, lets again assume a = -3 and b = -2. Just as above we still get a NO. Again choosing the same set for a = -3 and b = 2, we get a YES to the question stem. Insufficient.
Combining both, we know that b-a>0 and mod(a)-mod(b)>0. Thus lets choose a=-7 and b=-2. We get 1/(a-b) = -0.2 and a*b = 14. Thus a NO. Again, choosing b=3 and a=-5, we get a YES . Insufficient.
Basically, the two fact statements given together mean that (a+b)<0. It's because from F.S 1, we get a^2-b^2>0 or (a-b)*(a+b)>0. We have from F.S 2 that a-b<0. Thus, (a+b) has to be negative.
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
01 Jan 2014, 22:44
1
This post received KUDOS
Value substitution is good to solve this: 1. |a|>|b| we can say a can not be zero bcz mod of b will always be positive or equal to zero thus a must be anything but not zero.
We can do value substitution to test all cases: | a | b | a-b | 1/(a-b) | ab | Pass/ Fail for option (1) | -3 | -2 | -1 | -1 | 6 | Fail | -3 | 2 .| -5 | -1/5 | -6 | Pass | 3 .| 2 | 1 | 1 | 6 | Fail | 3 .| -2 | 5 | 1/5 | -6 | Pass | -3 .| 0 | -3 | -1/3 | 0 | Fail | 3 .| 0 | 3 | 1/3 | 0 | Pass
Multiple Pass / Fail inconsistent result, option one not sufficient.
Again inconsistent result, thus both option also not sufficient.
Answer E. _________________
Piyush K ----------------------- Our greatest weakness lies in giving up. The most certain way to succeed is to try just one more time. ― Thomas A. Edison Don't forget to press--> Kudos My Articles: 1. WOULD: when to use?| 2. All GMATPrep RCs (New) Tip: Before exam a week earlier don't forget to exhaust all gmatprep problems specially for "sentence correction".
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
18 Feb 2014, 02:10
(1) |a| > |b| Clearly IS. Look at this:
a > b -a > b - a > -b a > -b
Would give you various answers for the YES/NO Question. IS!
(2) a<b. Here, a could be 1 and b 2. then we had 1/-1 = -1 and 1 * 2 = 2. Hence 1/(a-b) < a*b. But if a = -1 and b = 2 then 1/(a-b) = -1/3 and a*b = -1 * 2 = -2. Thus 1/(a+b) > a*b. IS.
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
26 Apr 2014, 07:26
So let's see. I think fastest way is to pic numbers. Statement 1, let's first say a=-2, b=1 then we have a YES answer. Let's also say that a=2 and b=1 then we have a NO answer. Insufficient. Statement 2, we can use a=2 and b=1 again for a YES answer. For a NO answer we could use b=3 and a=1. Insufficient. Both statements together we have that we can still use a=-2 and b=1 for a YES answer. Additionally, we could also have that both 'a' amd 'b' are negative. As in a=-3 and b=-2, giving a NO answer.
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
30 Apr 2014, 12:07
Hey Karishma & Bunuel, Is there a faster way to solve this problem? I tried picking numbers but it took me more than 2 mins to arrive at the answer. Thanks, -Prasoon
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
30 Apr 2014, 23:58
1
This post received KUDOS
Expert's post
prsnt11 wrote:
Hey Karishma & Bunuel, Is there a faster way to solve this problem? I tried picking numbers but it took me more than 2 mins to arrive at the answer. Thanks, -Prasoon
For this problem I'd still advice to use number plugging at one point or another.
If a is not equal to b, is 1/(a-b) > ab ?
(1) |a| > |b|. This statement implies that a is further from 0 then b. We can have 4 cases:
For the second case the LHS is positive, while RHS is negative: 1/(a-b) > ab; For the fourth case the LHS is negative, while RHS is positive: 1/(a-b) < ab.
Two different answers. Not sufficient.
(2) a < b --> a - b < 0. The LHS is negative:
If a=-2 and b=1, then (1/(a-b)=-1/3) > (ab=-2); If a=-2 and b=-1, then (1/(a-b)=-1) < (ab=2).
Two different answers. Not sufficient.
(1)+(2) We can have only the third or fourth cases from (1):
--a-----0--b----- --a--b--0--------
We can use the same example as for (2): If a=-2 and b=1, then (1/(a-b)=-1/3) > (ab=-2); If a=-2 and b=-1, then (1/(a-b)=-1) < (ab=2).
Re: If a is not equal to b, is 1/(a-b) > ab ? [#permalink]
08 Sep 2015, 12:31
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. _________________
As I’m halfway through my second year now, graduation is now rapidly approaching. I’ve neglected this blog in the last year, mainly because I felt I didn’...
Perhaps known best for its men’s basketball team – winners of five national championships, including last year’s – Duke University is also home to an elite full-time MBA...
Hilary Term has only started and we can feel the heat already. The two weeks have been packed with activities and submissions, giving a peek into what will follow...