OG12 DS question 170

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OG12 DS question 170

by pramod_d » Sun Aug 08, 2010 7:07 am
Hi,

If n is a positive integer, is n3(cube) - n divisible by 4 ?
(1) n = 2k + 1, where k is an integer.
(2) n2 + n is divisible by 6.

Answer as per OG is A, 1 itself is sufficient but not 2.

However, for k = 0 (k is integer), n value is 1(positive) and n(cube) - n is 0 which is not divisible by 4. For all other cases it is divisible. So, A alone is not sufficient. In that case C will be the answer as it will prompt k value to be more than 0. Can some one tell me if there is anything wrong in my analysis?
Source: — Data Sufficiency |

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by selango » Sun Aug 08, 2010 7:33 am
0 is divided by all nonzero numbers.
--Anand--

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by mainhoon » Sun Aug 08, 2010 9:49 pm
pramod_d wrote:Hi,

If n is a positive integer, is n3(cube) - n divisible by 4 ?
(1) n = 2k + 1, where k is an integer.
(2) n2 + n is divisible by 6.

Answer as per OG is A, 1 itself is sufficient but not 2.

However, for k = 0 (k is integer), n value is 1(positive) and n(cube) - n is 0 which is not divisible by 4. For all other cases it is divisible. So, A alone is not sufficient. In that case C will be the answer as it will prompt k value to be more than 0. Can some one tell me if there is anything wrong in my analysis?
0 IS divisible by 4.

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by pramod_d » Wed Aug 11, 2010 8:11 am
mainhoon wrote:
pramod_d wrote:Hi,

If n is a positive integer, is n3(cube) - n divisible by 4 ?
(1) n = 2k + 1, where k is an integer.
(2) n2 + n is divisible by 6.

Answer as per OG is A, 1 itself is sufficient but not 2.

However, for k = 0 (k is integer), n value is 1(positive) and n(cube) - n is 0 which is not divisible by 4. For all other cases it is divisible. So, A alone is not sufficient. In that case C will be the answer as it will prompt k value to be more than 0. Can some one tell me if there is anything wrong in my analysis?
0 IS divisible by 4.
Thank you.