Is 1 / (a-b) < (b-a)?
(1) a < b
(2) 1 < |a-b|
For statement 1:
a,b = 2,3
a,b = -2,3
a,b = -10,-3
For all above pairs, I always get a YES for the question.
For statement 2:
I can rephrase the inequality as in 2 cases ( based on the approach stated in Manhattan book )
a-b > 1 or b-a < 1
For both cases, I took a and b as
a,b = 6,4
a,b = 3,-2
For all above pairs, I always get a NO for the question.
Is my approach in re-phrasing statement 2 wrong? GMAT Instructors, Please help.
DS problem - How to solve absolute inequalities?
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 63
- Joined: Sat Jul 24, 2010 10:29 am
- Thanked: 1 times
- Followed by:1 members
- GMAT Score:640
-
- Senior | Next Rank: 100 Posts
- Posts: 63
- Joined: Sat Jul 24, 2010 10:29 am
- Thanked: 1 times
- Followed by:1 members
- GMAT Score:640
- leonswati
- Senior | Next Rank: 100 Posts
- Posts: 94
- Joined: Sun Aug 29, 2010 3:40 am
- Thanked: 3 times
- Followed by:1 members
The way You solved statement 1 you can be sure that if a<b we will always get a yes...praveen_gmat wrote:Is 1 / (a-b) < (b-a)?
(1) a < b
(2) 1 < |a-b|
For statement 1:
a,b = 2,3
a,b = -2,3
a,b = -10,-3
For all above pairs, I always get a YES for the question.
For statement 2:
I can rephrase the inequality as in 2 cases ( based on the approach stated in Manhattan book )
a-b > 1 or b-a < 1
For both cases, I took a and b as
a,b = 6,4
a,b = 3,-2
For all above pairs, I always get a NO for the question.
Is my approach in re-phrasing statement 2 wrong? GMAT Instructors, Please help.
Now lets solve statement 2:
We can assume any value of |a-b|>1 , so let |a-b| = 2
therefore we can say that either
a-b = -2 ororororororor a-b = 2
a = b-2 orororororororo a = b+2
a<b orororororororororor a>b
So according to this the answer is either yes or no.....
So answer is A
-
- Senior | Next Rank: 100 Posts
- Posts: 63
- Joined: Sat Jul 24, 2010 10:29 am
- Thanked: 1 times
- Followed by:1 members
- GMAT Score:640
- sam2304
- Legendary Member
- Posts: 1239
- Joined: Tue Apr 26, 2011 6:25 am
- Thanked: 233 times
- Followed by:26 members
- GMAT Score:680
Its quite easier without substituting values.
Is 1 / (a-b) < (b-a)?
A. a < b
we can rewrite this as a-b < 0 => b-a > 0
so 1/-ve < +ve - true
SUFF
B. 1< |a-b|
this gives 2 inequalities
1 < a-b or 1 < -(a-b) = 1 < b-a = -1 > a-b
a-b > 1 or a-b < -1
If a-b > 1 => a-b is +ve, then b-a is -ve
So 1/+ve < -ve is false
If a-b < -1 => a-b is -ve, then b-a is +ve
So 1/-ve < +ve is true
INSUFF
So A
Is 1 / (a-b) < (b-a)?
A. a < b
we can rewrite this as a-b < 0 => b-a > 0
so 1/-ve < +ve - true
SUFF
B. 1< |a-b|
this gives 2 inequalities
1 < a-b or 1 < -(a-b) = 1 < b-a = -1 > a-b
a-b > 1 or a-b < -1
If a-b > 1 => a-b is +ve, then b-a is -ve
So 1/+ve < -ve is false
If a-b < -1 => a-b is -ve, then b-a is +ve
So 1/-ve < +ve is true
INSUFF
So A
Getting defeated is just a temporary notion, giving it up is what makes it permanent.
https://gmatandbeyond.blogspot.in/
https://gmatandbeyond.blogspot.in/