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# PS - True

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Director
Joined: 25 Oct 2006
Posts: 633

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24 Mar 2009, 21:42
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This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Which of the following about (1/11)+(1/12)+....+(1/20) is true?

A. >1/2
B. =1/2
C. =1/4
D. =1/8
E. <1/4

How to proceed??
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If You're Not Living On The Edge, You're Taking Up Too Much Space

Intern
Joined: 07 Feb 2009
Posts: 47

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24 Mar 2009, 23:16
1
KUDOS
My ans is A.

Explanation:
As, 1/11>1/20
Similarly, 1/12>1/20
.
.
.
1/19>1/20

hence,
(1/11)+(1/12)+....+(1/20) > (1/20)+(1/20)+....+(1/20)
or, Sum>10(1/20)
or, Sum>1/2
Director
Joined: 25 Oct 2006
Posts: 633

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25 Mar 2009, 09:15
absolutely, A.

Thanks for explanation.
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If You're Not Living On The Edge, You're Taking Up Too Much Space

Director
Joined: 25 Oct 2008
Posts: 591
Location: Kolkata,India

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02 Jul 2009, 03:25
super cool explanation!!
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http://gmatclub.com/forum/countdown-beginshas-ended-85483-40.html#p649902

Director
Joined: 27 Jun 2008
Posts: 538
WE 1: Investment Banking - 6yrs

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02 Jul 2009, 04:04
abhishekik wrote:
My ans is A.

Explanation:
As, 1/11>1/20
Similarly, 1/12>1/20
.
.
.
1/19>1/20

hence,
(1/11)+(1/12)+....+(1/20) > (1/20)+(1/20)+....+(1/20)
or, Sum>10(1/20)
or, Sum>1/2

+1 good explanation

Also, logically

we can eliminate C & D...can never be equal to 0.25 & 0.125.
E - we can eliminate because the answer cannot be less than 0.25.
1/11 = 0.0909
1/20 = 0.0025..both nearly adds to 0.0934, besides, you also have 8 more numbers inbetween, so it obvious that it cannot be less than 0.25.
B - GMAT wouldnt want us to calculate the exact number, if we did, this would take more than 2-3 mins to solve. Eliminate.
Hence, A

A. >1/2
B. =1/2
C. =1/4
D. =1/8
E. <1/4
Re: PS - True   [#permalink] 02 Jul 2009, 04:04
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