Last visit was: 23 Nov 2024, 15:18 It is currently 23 Nov 2024, 15:18

Close

GRE Prep Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GRE score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel
Verbal Expert
Joined: 18 Apr 2015
Posts: 30016
Own Kudos [?]: 36366 [10]
Given Kudos: 25928
Send PM
avatar
Director
Director
Joined: 03 Sep 2017
Posts: 518
Own Kudos [?]: 703 [3]
Given Kudos: 0
Send PM
avatar
Intern
Intern
Joined: 08 Dec 2017
Posts: 40
Own Kudos [?]: 69 [0]
Given Kudos: 0
Send PM
Target Test Prep Representative
Joined: 09 May 2016
Status:Head GRE Instructor
Affiliations: Target Test Prep
Posts: 183
Own Kudos [?]: 276 [2]
Given Kudos: 114
Location: United States
Send PM
Re: In a sequence a1, a2,…, each term after the first is found [#permalink]
2
Expert Reply
Carcass wrote:

This question is part of GREPrepClub - The Questions Vault Project



In a sequence a1, a2,…, each term after the first is found by taking the negative of the preceding term, and adding 1. If a1 = 2, what is the sum of the first 99 terms?

(A) 49
(B) 50
(C) 51
(D) 99
(E) 101


a1 = 2

a2 = -1

a3 = 2

a4 = -1

a5 = 2

a6 = -1

We see that each odd/even pair sums to positive 1.

There are 49 even/odd pairs in the first 98 terms; hence, the sum is 49. Since a99 is an odd-numbered term, a99 = 2. So the sum of the first 99 terms is 49 + 2 = 51.

Answer: C
Intern
Intern
Joined: 30 Aug 2021
Posts: 25
Own Kudos [?]: 11 [0]
Given Kudos: 12
Send PM
Re: In a sequence a1, a2,…, each term after the first is found [#permalink]
i have a doubt how are there 50 odd terms in the first 99 terms. Please elaborate cause when they mention first 99 terms do they mean inclusive or exclusive and also when they mention first 99 terms is the 100th number also included?
User avatar
GRE Prep Club Legend
GRE Prep Club Legend
Joined: 07 Jan 2021
Posts: 5043
Own Kudos [?]: 74 [0]
Given Kudos: 0
Send PM
Re: In a sequence a1, a2,, each term after the first is found [#permalink]
Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Prep Club for GRE Bot
Re: In a sequence a1, a2,, each term after the first is found [#permalink]
Moderators:
GRE Instructor
84 posts
GRE Forum Moderator
37 posts
Moderator
1111 posts
GRE Instructor
234 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne