If a and b are positive, is (a^-1 + b^-1) less than : GMAT Data Sufficiency (DS)
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# If a and b are positive, is (a^-1 + b^-1) less than

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Manager
Joined: 04 Aug 2011
Posts: 51
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Kudos [?]: 23 [0], given: 0

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

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20 Aug 2011, 04:03
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Question Stats:

0% (00:00) correct 100% (03:57) wrong based on 2 sessions

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

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

I chose D
[Reveal] Spoiler: OA
Manager
Joined: 18 Aug 2011
Posts: 60
Followers: 1

Kudos [?]: 35 [0], given: 6

Re: a GWD math (5) , which hasn't been discussed [#permalink]

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20 Aug 2011, 09:06
Jasontuyj2012 wrote:
If a and b are positive, is (a^-1 + b^-1) less than (a^-1*b^-1)^-1

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

I chose D

D is not possible, because A is insufficient.

Try 4|2 and 0.5|0.25 respectively, both will give you different results.

I guessed C, because I ran out of time

Rewriting the expression in the first place might be clever:

(b+a)/(ab) < ab should be the same expression.
Manager
Joined: 16 May 2011
Posts: 204
Concentration: Finance, Real Estate
GMAT Date: 12-27-2011
WE: Law (Law)
Followers: 1

Kudos [?]: 76 [0], given: 37

Re: a GWD math (5) , which hasn't been discussed [#permalink]

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20 Aug 2011, 11:57
well, after trying to solve it's seems there is a TYPO: it should be (a^-1+ b^-1)^-1

here is a discussion:

if-a-and-b-are-positive-106509.html
Re: a GWD math (5) , which hasn't been discussed   [#permalink] 20 Aug 2011, 11:57
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