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

Redeem

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.

★★★★★5.0559 reviews
GMATBootcamp Starts Sep 21
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE BOOTCAMP

Live Online Bootcamp Class with Top GMAT Expert Chris Peckover

Sep 21 to Oct 9, 2026

Schedule
Mon to Fri · 7:00 to 10:00 PM ET
Included
Live classes + 6 months of TTP OnDemand
  • Boost your GMAT score in less than one month in a live online class
  • 6 months access to TTP OnDemand video courses included
View bootcamp & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
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
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start 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 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

trouble with sequence

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 71
Joined: Sat Sep 20, 2008 5:48 am
Thanked: 5 times
by willbeatthegmat » Wed Jan 21, 2009 8:01 am
Q- The infinite sequence a1, a2,…, an,… is such that a1 = 2, a2 = -3, a3 = 5, a4 = -1, and an = an-4 for n > 4. What is the sum of the first 97 terms of the sequence?

A. 72
B. 74
C. 75
D. 78
E. 80
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 259
Joined: Thu Jan 18, 2007 8:30 pm
Thanked: 16 times

by amitabhprasad » Wed Jan 21, 2009 8:35 am
I am getting answer as 74 ?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 129
Joined: Mon Dec 15, 2008 11:43 pm
Location: Hyderabad
Thanked: 2 times

by naaga » Wed Jan 21, 2009 8:41 am
amitabh can you please explain in detail .....
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 259
Joined: Thu Jan 18, 2007 8:30 pm
Thanked: 16 times

by amitabhprasad » Wed Jan 21, 2009 8:52 am
naaga wrote:amitabh can you please explain in detail .....
Sure,
a1 = 2, a2 = -3, a3 = 5, a4 = -1
==> a1+a2+a3+a4 = 3
now we have an = an-4
==> a5 = a5-4 = a1=2
a6 = a6-4 =a2 = -3
a7 = a7-4 = a3 = 5
a8 = a8-4 = a4 = -1
and so on you will see we get sequence in the block of 4
We are supposed to find the sum of first 97 terms
so sum of 97 terms = 24*(sum of 1st 4 terms )+1st term
=24*3+2 = 74
HTH
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 138
Joined: Thu Jan 15, 2009 7:52 am
Location: Steamboat Springs, CO
Thanked: 15 times

by gaggleofgirls » Thu Jan 22, 2009 10:29 am
For the infinite sequence, the terms 2, -3, 5, -1 repeat infinitely.

2 + -3 + 5 -1 = 3, so the sum for every set of the 4 numbers is 4.

How many sets of these 4 numbers are there in the first 97 terms?

97/4 = 24 remainder 1

So, first let's address the 24. There are 24 sets of numbers whose sum is 3 in the first 97 terms, 24 * 3 = 72.

But now you have to address the remainder 1, there is 1 more number in the sequence, and it will be the next number in line, which is the first number of the set of 4, which is a1, which is 2.

So, the answer is 72 +2 = 74

Answer is B

-Carrie
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1