number of element of the set

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adam15: Senior | Next Rank: 100 Posts; Posts: 70; Joined: Mon May 12, 2008 12:26 pm; Thanked: 3 times

by adam15 » Sat Nov 21, 2009 7:38 pm

The sum of n consecutive positive integers is 45. What is the value of n?

(1) n is even

(2) n < 9
the answer will be posted after discussion thanks

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Source: Beat The GMAT — Data Sufficiency | Sat Nov 21, 2009 7:38 pm

brick2009: Master | Next Rank: 500 Posts; Posts: 171; Joined: Mon Jun 01, 2009 8:59 pm; Thanked: 8 times

by brick2009 » Sat Nov 21, 2009 8:31 pm

Ans is : E

a.) n is even
22,23 => n = 2
5,6,7,8,9,10 => n=6
-----------> Insuff.

b.) n<9
1,2,3,4,5,6,7,8,9 = 45 , but n = 9

only other would be : n= 2 (22,23)
n = 6 (5 to 10)

--------> insuff

Thus, E

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adam15: Senior | Next Rank: 100 Posts; Posts: 70; Joined: Mon May 12, 2008 12:26 pm; Thanked: 3 times

by adam15 » Sat Nov 21, 2009 8:59 pm

well done.

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Thu Dec 03, 2009 6:52 pm

Did you try adding a few numbers randomly? Is there a formula that you used or a method?

brick2009 wrote:Ans is : E

a.) n is even
22,23 => n = 2
5,6,7,8,9,10 => n=6
-----------> Insuff.

b.) n<9
1,2,3,4,5,6,7,8,9 = 45 , but n = 9

only other would be : n= 2 (22,23)
n = 6 (5 to 10)

--------> insuff

Thus, E

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