Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Series

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Fri Jan 28, 2011 12:36 am
Thanked: 1 times
by diehard_gmat » Thu Feb 03, 2011 7:57 am
Consider the sequence 1, -2, 3, -4, 5, -6, ..... , whose n-th term is [(-1)^(n+1)]*(n). What is the average of the first 200 terms of the sequence?

A) -1
B) -0.5
C) 0
D) 0.5
E) 1
Top
Join the discussion
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members
Location: Milpitas, CA
Thanked: 1854 times
GMAT Score:770

by Anurag@Gurome » Thu Feb 03, 2011 7:59 am
diehard_gmat wrote:Consider the sequence 1, -2, 3, -4, 5, -6, ..... , whose n-th term is [(-1)^(n+1)]*(n). What is the average of the first 200 terms of the sequence?

A) -1
B) -0.5
C) 0
D) 0.5
E) 1
Note that the sum of alternate pairs of the series taken in order is -1.
There are 100 such pairs in the first 200 terms. Sum of each pair is -1.
Hence, sum of 200 terms = (-1)*(100) = -100

Hence, average = (-100)/200 = -0.5

The correct answer is B
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 131
Joined: Fri Jun 18, 2010 10:19 am
Location: New York, NY
Thanked: 10 times

by aleph777 » Fri Feb 04, 2011 6:25 am
Maybe not as technical as Anurag's explanation, but since I knew this was an average problem, I knew I could find the average using the formula largest number + smallest number / 2. After plugging in 200 into the formula, though, and pulling out -200, I realized that would have to be the lowest. I looked back at the original pattern, and noticed every odd digit was positive, and every even digit was negative, so if -200 is the SMALLEST number, then by plugging in 199, you'd find the largest digit (which is just 199, after computation).

So then I simply plugged these two into the standard average formula:

[199 + (-200)]/2 = -0.5
Top
Join the discussion