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# Progression

Author Message
Intern
Joined: 12 Apr 2010
Posts: 13

Kudos [?]: 19 [0], given: 0

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25 Apr 2010, 12:22
00:00

Difficulty:

(N/A)

Question Stats:

100% (01:06) correct 0% (00:00) wrong based on 4 sessions

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The Sum of 3rd & 15th elements of an AP is equal to the sum of 6th 11th &13th elements of the same AP then which of the series should necessarily be equal to zero.

a)1st
b)9th
c)12th
d)3rd
e)15th

Kudos [?]: 19 [0], given: 0

CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2764

Kudos [?]: 1856 [0], given: 235

Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35

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25 Apr 2010, 12:27
ISB2011 wrote:
The Sum of 3rd & 15th elements of an AP is equal to the sum of 6th 11th &13th elements of the same AP then which of the series should necessarily be equal to zero.

a)1st
b)9th
c)12th
d)3rd
e)15th

IMO C

as per question take 1st term as a and difference as d

a+2d + a+14d = a+5d + a+10d + a+12d

=> a+11d = 0 which is the 12th term
a+11d = a+(n-1)d => n-1 = 11 => n =12
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Kudos [?]: 1856 [0], given: 235

Re: Progression   [#permalink] 25 Apr 2010, 12:27
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