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

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Intern
Intern
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Joined: 04 Aug 2011
Posts: 49

Kudos [?]: 33 [0], given: 0

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

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New post 20 Aug 2011, 05:03
00:00
A
B
C
D
E

Difficulty:

(N/A)

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

Kudos [?]: 33 [0], given: 0

Manager
Manager
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Joined: 18 Aug 2011
Posts: 59

Kudos [?]: 45 [0], given: 6

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

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New post 20 Aug 2011, 10:06
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 :cry:

Rewriting the expression in the first place might be clever:

(b+a)/(ab) < ab should be the same expression.

Kudos [?]: 45 [0], given: 6

Manager
Manager
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Joined: 16 May 2011
Posts: 203

Kudos [?]: 98 [0], given: 37

Concentration: Finance, Real Estate
GMAT Date: 12-27-2011
WE: Law (Law)
GMAT ToolKit User
Re: a GWD math (5) , which hasn't been discussed [#permalink]

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New post 20 Aug 2011, 12:57
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

Kudos [?]: 98 [0], given: 37

Re: a GWD math (5) , which hasn't been discussed   [#permalink] 20 Aug 2011, 12:57
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If a and b are positive, is (a^-1 + b^-1) less than

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