BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Given a series of n consecutive positive integers . . .

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 2898
Joined: Thu Sep 07, 2017 2:49 pm
Thanked: 6 times
Followed by:5 members

Given a series of n consecutive positive integers . . .

by Vincen » Tue Nov 28, 2017 8:14 am
Given a series of n consecutive positive integers, where n > 1, is the average value of this series an integer divisible by 3?

(1) n is odd
(2) The sum of the first number of the series and (n - 1) / 2 is an integer divisible by 3

The OA is B .

I thought the answer was D. Experts, may you assist me here?
Top
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
Legendary Member
Posts: 503
Joined: Thu Jul 20, 2017 9:03 am
Thanked: 86 times
Followed by:15 members
GMAT Score:770

by ErikaPrepScholar » Tue Nov 28, 2017 2:44 pm
We can evaluate Statement 1 by plugging in smart numbers to try to prove that it is insufficient. To do this, we want to find one case where the average is divisible by 3 and one case where the average is not divisible by 3.

Say the first value in the series is 1 and n = 3. Then the series is 1, 2, 3, and the average is 2, which is not divisible by 3.
Say the first value in the series is 2 and n = 3. Then the series is 2, 3, 4 and the average is 3, which IS divisible by 3.

So Statement 1 is insufficient.
Image

Erika John - Content Manager/Lead Instructor
https://gmat.prepscholar.com/gmat/s/

Get tutoring from me or another PrepScholar GMAT expert: https://gmat.prepscholar.com/gmat/s/tutoring/

Learn about our exclusive savings for BTG members (up to 25% off) and our 5 day free trial

Check out our PrepScholar GMAT YouTube channel, and read our expert guides on the PrepScholar GMAT blog
Top
Post new topic Post Reply
• Page 1 of 1