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 GMAT 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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

S is an infinite sequence, in which the value of a [#permalink]
23 Sep 2011, 22:23

1

This post received KUDOS

3

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

95% (hard)

Question Stats:

23% (02:03) correct
77% (01:22) wrong based on 207 sessions

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

(1) The 1st term is 1. (2) The 3rd term is 3.

St1: t1 = 1 Let t2 = x t3 = t2-t1= x-1 ( difference between the two preceding members of the sequence) t4 = t3-t2 = x-1-x = -1 t5 = t4-t3 = -1-x+1= -x t6 = t5 -t4 = -x+1 = 1-x t7 = t6-t5 = 1-x+x = 1

If u carefully see , this follows are particular pattern; first 3 terms , then next 3 ( but negative).. this is symmetry .. and will continue ( t7 will start again with 1) hence t 7 = 1 t 13 = 1 t19=1 t25= 1 t31= 1 t 37= 1 t 43 = 1

Re: DS Question - Sequences [#permalink]
08 May 2013, 19:45

sudhir18n wrote:

gmatprep2011 wrote:

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

(1) The 1st term is 1. (2) The 3rd term is 3.

St1: t1 = 1 Let t2 = x t3 = t2-t1= x-1 ( difference between the two preceding members of the sequence) t4 = t3-t2 = x-1-x = -1 t5 = t4-t3 = -1-x+1= -x t6 = t5 -t4 = -x+1 = 1-x t7 = t6-t5 = 1-x+x = 1

If u carefully see , this follows are particular pattern; first 3 terms , then next 3 ( but negative).. this is symmetry .. and will continue ( t7 will start again with 1) hence t 7 = 1 t 13 = 1 t19=1 t25= 1 t31= 1 t 37= 1 t 43 = 1

Hence statement 1 : sufficient

St 2: not much of help .

hence its A.

I could get to the answer, but took almost 2:30 to evaluate both the options. Can anyone please provide a quicker solution?

Re: DS Question - Sequences [#permalink]
28 May 2013, 07:35

With the above assumption, "C" would be the answer.

But, if the question were written like this:

S is an infinite sequence, in which each term \(S_n=S_{(n-1)}-S_{(n-2)}\), such that n>=3. What is the value of the 43rd member of the sequence?

1. \(S_1=1\) 2. \(S_3=3\)

Why would the answer be c? you could have a sequence: 1,-2,3 or you could have 1,4,3. So the fourth term would be different in these two cases!! What is the source of this question?? Answer would be A as nicely explained by sudhir18n.[/quote]

Re: S is an infinite sequence, in which the value of a [#permalink]
28 May 2013, 09:13

2

This post received KUDOS

Expert's post

2

This post was BOOKMARKED

gmatprep2011 wrote:

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

Re: S is an infinite sequence, in which the value of a [#permalink]
03 Jul 2013, 07:04

Hello.. Can we say that as the question stands now, the answer is "E". I feel so as there is no way to know whether t3= t2-t1 or t3= t1-t2.... Thanks in advance!

S is an infinite sequence, in which the value of a [#permalink]
21 Sep 2014, 08:56

Bunuel wrote:

gmatprep2011 wrote:

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

Re: S is an infinite sequence, in which the value of a [#permalink]
21 Sep 2014, 10:41

Expert's post

gauravkaushik8591 wrote:

Bunuel wrote:

gmatprep2011 wrote:

S is an infinite sequence, in which the value of a particular member of the sequence is equal to the difference between the two preceding members of the sequence. What is the value of the 43rd member of the sequence?

I am not panicking. Nope, Not at all. But I am beginning to wonder what I was thinking when I decided to work full-time and plan my cross-continent relocation...

Over the last week my Facebook wall has been flooded with most positive, almost euphoric emotions: “End of a fantastic school year”, “What a life-changing year it’s been”, “My...