DS Question - 6

Give that n is an integer, is n-1 divisible by 3?

1. n^2 +n is not divisible by 3

2. 3n+5>=k+8, where k is a positive multiple of 3

Answer - A

Sttement (1) Sufficient -- It can be simplified as n(n+1) is not divisible by 3

i.e to satisfy the above condition n can take a value immediately following 3 or multiples of 3.

Such as n = 4, 7, 10 .....

Thus case n-1 is always divisible by 3.

Statement (2) Insufficient -- 3n >= k + 3

This implies n >= (k+3)/3

the possible values of k includes 3,6,9,12 .....

So this can be either multiple of 3 or any other number..