If n = 3k, is k an integer?
(1) n is an integer.
(2) n/6 is an integer.
OA=B
Source: GMAT Prep
Hi Vjesus12.
We need to determine if k is an integer or not. So, let's do it.
First, let's rewrite the given expression as $$n=3k\ \ \ \ \Rightarrow\ \ \ k=\frac{n}{3}.$$
Statement 1
(1) n is an integer.
We have two cases:
(i) If n is a multiple of 3, then k is an integer.
(ii) If n is not a multiple of 3 (for example, n=2), then k is not an integer.
So, this statement is
NOT SUFFICIENT.
Statement 2
(2) n/6 is an integer.
Here we have that $$\frac{n}{6}=p\ \ \ \Rightarrow\ n=6\cdot p\ \ \ \ \Rightarrow\ \ \ n=3\cdot2\cdot p,\ \ \ \ \ \ p\in\mathbb{Z}.$$ So, we get $$k=\frac{n}{3}=\frac{3\cdot2\cdot p}{3}=2\cdot p\ \in\mathbb{Z}\ \ .$$ So, k is an integer. Therefore, this statement is
SUFFICIENT.
Hence, the correct answer is the option
_B_.
I hope it helps you.