Is positive integer n 1 a multiple of 3? (1) n^3 n is a

Question

Is positive integer n – 1 a multiple of 3?

(1) n^3 – n is a multiple of 3

(2) n^3 + 2n^2+ n is a multiple of 3

wudy · Answer

Sorry, I made a mistake. B is right. (2) n^3+2n^2+n=n*(n+1)^2 --> n=3a or n=3a-1, where a is a positive integer --> n-1= 3a-1 or n-1=3a-2, none of which is a multiple of 3. --> Sufficient. The exaplanation relates to the link below: https://www.gmatclub.com/phpbb/viewtopic.php?t=48376.

plaguerabbit · Answer

i'll go with B here too

S2: n(n+1)^2

this means either n or n+1 is a mult of 3. if this is the case, there is no way n-1 can be a mult of 3.

trahul4 · Answer

I will go with E. Picking up numbers will help. Pick up n =3 and you will see both statements are insuff.

plaguerabbit · Answer

What is an example for S2 where the answer is yes?

wudy · Answer

Please check the above link. E is not the answer, although at first I got E too. :oops:

dreamgmat1 · Answer

OA is B

Any three consecutive positive integers include exactly one multiple of 3

Is positive integer n 1 a multiple of 3? (1) n^3 n is a

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