Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 22 May 2017, 15:09

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If a and b are positive, is (a^-1 + b^-1)^-1 less than

Author Message
VP
Joined: 06 Jun 2004
Posts: 1057
Location: CA
Followers: 2

Kudos [?]: 159 [0], given: 0

If a and b are positive, is (a^-1 + b^-1)^-1 less than [#permalink]

### Show Tags

28 May 2006, 23:49
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 1 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If a and b are positive, is (a^-1 + b^-1)^-1 less than (a^-1*b^-1)^-1?

(1) a = 2b
(2) a + b > 1
_________________

Don't be afraid to take a flying leap of faith.. If you risk nothing, than you gain nothing...

VP
Joined: 07 Nov 2005
Posts: 1123
Location: India
Followers: 5

Kudos [?]: 42 [0], given: 1

### Show Tags

29 May 2006, 00:24
Both the statements are sufficient in themselves.

The equation becomes :

{ (a * b) / (a + b ) } < (a * b)

Thus if :
a) a = 2b,
then eqn is ==> ( (2/3) * b) < (2 * b^2) which is true.

b) a + b=1, then LHS and RHS become equal.

Last edited by buzzgaurav on 29 May 2006, 01:11, edited 2 times in total.
VP
Joined: 07 Nov 2005
Posts: 1123
Location: India
Followers: 5

Kudos [?]: 42 [0], given: 1

### Show Tags

29 May 2006, 01:12
shobhitb wrote:
buzzgaurav wrote:
Both the statements are sufficient in themselves.

The equation becomes :

{ (a * b) / (a + b ) } < (a * b)

Thus if :
a) a = 2b,
then eqn is ==> b < (2 * b^2) which is true.

b) a + b=1, then also LHS is smaller than RHS due to a factor (a + b) in the denominator of LHS.

I am getting B

Sorry for the mistake in the original post, but I am still getting B.
I might be wrong as I am not at all good at quant
VP
Joined: 21 Sep 2003
Posts: 1060
Location: USA
Followers: 3

Kudos [?]: 79 [0], given: 0

### Show Tags

29 May 2006, 06:21
Is ab/(a+b) < ab? given a and b are positive...
This is only possible if Denominator a+b > 1

2. SUFF.
1. If a+b < 1, say a = 0.2 and b = 0.1 , answer is No
if a+b > 1, say a = 2 , b=1, answer is Yes.
INSUFF.

B iti is!
_________________

"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."

- Bernard Edmonds

Director
Joined: 10 Oct 2005
Posts: 526
Location: US
Followers: 1

Kudos [?]: 63 [0], given: 0

### Show Tags

29 May 2006, 08:12
Yeah. B is the answer. Try plugging in 0.1 and 5 for a where a=2b and we can eliminate the answer.
VP
Joined: 06 Jun 2004
Posts: 1057
Location: CA
Followers: 2

Kudos [?]: 159 [0], given: 0

### Show Tags

29 May 2006, 11:30
OA is indeed B.

Great explanation Giddi
_________________

Don't be afraid to take a flying leap of faith.. If you risk nothing, than you gain nothing...

SVP
Joined: 14 Dec 2004
Posts: 1693
Followers: 3

Kudos [?]: 145 [0], given: 0

### Show Tags

29 May 2006, 19:19
"B" it is.

Girish, I really appreciate your approach to problems
29 May 2006, 19:19
Display posts from previous: Sort by