n divisible by 6?

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crackgmat007: Legendary Member; Posts: 882; Joined: Fri Feb 20, 2009 2:57 pmFollowed by: 1 member; Thanked: 15 times; GMAT Score:690

by crackgmat007 » Wed May 13, 2009 9:08 pm

If n and k are positive integers, is n divisible by 6?
(1) n = k(k + 1)(k - 1)
(2) k – 1 is a multiple of 3.

Is statement 1 alone is sufficient? Can anyone clarify this pls? Tx much.

Last edited by crackgmat007 on Mon May 18, 2009 10:48 am, edited 1 time in total.

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Source: Beat The GMAT — Data Sufficiency | Wed May 13, 2009 9:08 pm

aj5105: Legendary Member; Posts: 1169; Joined: Sun Jul 06, 2008 2:34 amFollowed by: 1 member; Thanked: 25 times

by aj5105 » Wed May 13, 2009 10:31 pm

Statement (1): You cannot consider 0,1,2. Though 1,2 are positive, the product (n) becomes 0.

Consider any three consecutive numbers[ k-1, k, k+1] such as 1, 2, 3 or 2, 3, 4 or 4, 5, 6 ... Their product is divisible by 6.

(A)

Last edited by aj5105 on Fri May 15, 2009 7:23 pm, edited 1 time in total.

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mike22629: Master | Next Rank: 500 Posts; Posts: 322; Joined: Fri Mar 27, 2009 3:56 pm; Thanked: 24 times; GMAT Score:710

by mike22629 » Fri May 15, 2009 9:28 am

You can also consider k=1

0 is divisible by any number or 0 is a multiple of every number.

IMO B.

Furthermore, think of the equation in the first statement

It is telling you that n = the product of three consecutive numbers

A number is divisible by 6 is it is divisible by 3 and by 2. Three consecutive positive numbers will always meet this requirement.

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iamcste: Legendary Member; Posts: 940; Joined: Tue Aug 26, 2008 3:22 amFollowed by: 1 member; Thanked: 55 times

by iamcste » Fri May 15, 2009 1:41 pm

mike22629 wrote:You can also consider k=1

0 is divisible by any number or 0 is a multiple of every number.

IMO B.

Furthermore, think of the equation in the first statement

It is telling you that n = the product of three consecutive numbers

A number is divisible by 6 is it is divisible by 3 and by 2. Three consecutive positive numbers will always meet this requirement.

IMO AHow can it be B

In Stmt 2, we have only information only about K. How does it help you to determine divisibility of n by 6. means you considered information stated in stmt 1 without knowing

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iamcste: Legendary Member; Posts: 940; Joined: Tue Aug 26, 2008 3:22 amFollowed by: 1 member; Thanked: 55 times

by iamcste » Fri May 15, 2009 1:46 pm

mike22629 wrote:You can also consider k=1

0 is divisible by any number or 0 is a multiple of every number.

.

when you select K=1, n becomes 0...and as per info given, n is a positive integer...and hence it cant be 0, Note: 0 is neither positive nor negative

HTH

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