If n = 3k, is k an integer?

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Vincen: Legendary Member; Posts: 2898; Joined: Thu Sep 07, 2017 2:49 pmFollowed by: 5 members; Thanked: 6 times

by Vincen » Tue Dec 26, 2017 5:07 am

If n = 3k, is k an integer?

(1) n is an integer.

(2) n/6 is an integer.

The OA is the option B.

Why is the statement (1) not sufficient? And how can I show that the statement (2) is sufficient? Experts, may you give me some help? Thanks in advanced.

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Source: Beat The GMAT — Data Sufficiency | Tue Dec 26, 2017 5:07 am

elias.latour.apex: Master | Next Rank: 500 Posts; Posts: 228; Joined: Thu Apr 20, 2017 1:02 amFollowed by: 3 members; Location: Global; Thanked: 32 times; GMAT Score:770

by elias.latour.apex » Wed Dec 27, 2017 8:03 pm

When doing data sufficiency, it is best to start off by asking ourselves: "What do we need?"

If N is 3k, is k an integer? Well, we need to know whether N is a multiple of 3. If it is (3,6,9) then k will be an integer. If not, then k will not be an integer.

Statement 1. Does this tell us whether N is a multiple of 3? No.
Statement 2. Does this tell us whether N is a multiple of 3? Yes. If N is evenly divisible by 6, then it must be evenly divisible by both 2 and 3.

Therefore, statement 2 alone is sufficient. (B)

Elias Latour
Verbal Specialist @ ApexGMAT
blog.apexgmat.com
+1 (646) 736-7622

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