Sequence

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MBA.Aspirant: Master | Next Rank: 500 Posts; Posts: 401; Joined: Tue May 24, 2011 1:14 amFollowed by: 5 members; Thanked: 37 times

by MBA.Aspirant » Fri Jun 24, 2011 1:41 pm

A sequence repeats as shown: -5,0,5,-5,0,5,-5,0,5. What's the sum of 250th and 251st term?

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Source: Beat The GMAT — Problem Solving | Fri Jun 24, 2011 1:41 pm

galaxian: Senior | Next Rank: 100 Posts; Posts: 79; Joined: Mon Jan 17, 2011 4:51 amFollowed by: 5 members; Location: Hyderabad, India; Thanked: 8 times

by galaxian » Fri Jun 24, 2011 3:00 pm

If you divide the sequence into sub seq with 3 nos. -5,0,5 the sum is 0.
When you come to 250th term, it would be a part of the sequence :

250th, 251st & 252th term = -5,0 & 5.
So Ans should be -5.

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edvhou812: Master | Next Rank: 500 Posts; Posts: 143; Joined: Sat Nov 06, 2010 9:06 pmFollowed by: 1 member; Thanked: 10 times

by edvhou812 » Fri Jun 24, 2011 10:21 pm

Assume that the 250th term is the beginning of new set, check by dividing 249 by 3 and find that there are 83 sets before the 250 term, so 250th term must be -5. -5+0 = -5

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