Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 04 Oct 2015, 02:35

### GMAT 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# An infinite sequence of positive integers is called a

Author Message
TAGS:
Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 553
Location: United Kingdom
GMAT 1: 730 Q49 V40
GPA: 2.9
WE: Information Technology (Consulting)
Followers: 43

Kudos [?]: 1471 [2] , given: 217

An infinite sequence of positive integers is called a [#permalink]  13 Feb 2012, 16:14
2
KUDOS
3
This post was
BOOKMARKED
00:00

Difficulty:

55% (hard)

Question Stats:

46% (01:49) correct 54% (00:48) wrong based on 282 sessions
An infinite sequence of positive integers is called a coprime sequence if no term in the sequence shares a common divisor (except 1) with any other term in the sequence. If S is an infinite sequence of distinct positive integers, is S a coprime sequence?

(1) An infinite number of integers in S are prime.
(2) Each term in S has exactly two factors.

[Reveal] Spoiler:
Struggling to understand the answer as B.

Considering statement 1

If integers in S are prime they have exactly two factors and therefore this statement is same as B and therefore should be sufficient.

Where I am not getting this right guys?
[Reveal] Spoiler: OA

_________________

Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Math Expert
Joined: 02 Sep 2009
Posts: 29679
Followers: 4889

Kudos [?]: 53124 [3] , given: 8043

Re: An infinite sequence of positive integers is called a [#permalink]  13 Feb 2012, 18:07
3
KUDOS
Expert's post
2
This post was
BOOKMARKED
An infinite sequence of positive integers is called a coprime sequence if no term in the sequence shares a common divisor (except 1) with any other term in the sequence. If S is an infinite sequence of distinct positive integers, is S a coprime sequence?

Notice that S is an infinite sequence of distinct positive integers.

(1) An infinite number of integers in S are prime --> obviously these primes will be coprime to each other. But we don't know whether the sequence contains some numbers other than primes, and if it does then the sequence won't be coprime (for example the sequence can contain 4 and 6 in addition to these primes). Not Sufficient.

(2) Each term in S has exactly two factors --> each term in S is a prime, so S contains only distinct primes, which will be coprime. Sufficient.

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 29679
Followers: 4889

Kudos [?]: 53124 [0], given: 8043

Re: An infinite sequence of positive integers is called a [#permalink]  05 Sep 2013, 05:39
Expert's post
Bumping for review and further discussion.
_________________
Manager
Joined: 25 Oct 2013
Posts: 173
Followers: 1

Kudos [?]: 34 [0], given: 56

Re: An infinite sequence of positive integers is called a [#permalink]  08 Feb 2014, 03:38
Nice, nice nice. Fell into trap and chose wrong answer. Statement 1 seems like each number in s is prime but it is not! Statement 2 makes it look like the numbers are not prime but indeed they are!
_________________

Click on Kudos if you liked the post!

Practice makes Perfect.

Manager
Joined: 28 Jul 2013
Posts: 93
Location: India
Concentration: Marketing, Strategy
GPA: 3.62
WE: Engineering (Manufacturing)
Followers: 0

Kudos [?]: 24 [0], given: 37

Re: An infinite sequence of positive integers is called a [#permalink]  16 Apr 2015, 17:53
Bunuel: if two terms are 2 in the sequence S....(2,2,3,4,5..............) here the two terms have 2 as a common divisor. The question says that a coprime sequence will not have any other factor common to any other number except 1.
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 5953
Location: Pune, India
Followers: 1522

Kudos [?]: 8371 [0], given: 192

Re: An infinite sequence of positive integers is called a [#permalink]  17 Apr 2015, 00:49
Expert's post
sayansarkar wrote:
Bunuel: if two terms are 2 in the sequence S....(2,2,3,4,5..............) here the two terms have 2 as a common divisor. The question says that a coprime sequence will not have any other factor common to any other number except 1.

You are given that S has distinct integers. So two terms cannot be 2 each.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Manager Joined: 28 Jul 2013 Posts: 93 Location: India Concentration: Marketing, Strategy GPA: 3.62 WE: Engineering (Manufacturing) Followers: 0 Kudos [?]: 24 [0], given: 37 Re: An infi nite sequence of positive integers is called a [#permalink] 17 Apr 2015, 00:57 Thanks Karishma....You have discovered my other problem....I tend to read super fast and miss things in the process....my biggest weakness... Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 5953 Location: Pune, India Followers: 1522 Kudos [?]: 8371 [0], given: 192 Re: An infi nite sequence of positive integers is called a [#permalink] 17 Apr 2015, 01:03 Expert's post sayansarkar wrote: Thanks Karishma....You have discovered my other problem....I tend to read super fast and miss things in the process....my biggest weakness... Reading super fast is great for RC. For all others, it is not advisable. You have enough time so slow down a bit. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

Veritas Prep Reviews

Re: An infinite sequence of positive integers is called a   [#permalink] 17 Apr 2015, 01:03
Similar topics Replies Last post
Similar
Topics:
3 An infinite sequence of positive integers is called a "beta 4 01 May 2013, 09:08
An infinite sequence of positive integers is called a 3 06 Jun 2012, 18:33
16 An infinite sequence of positive integers is called a 10 16 Feb 2012, 15:11
13 S is an infinite sequence, in which the value of a 9 23 Sep 2011, 22:23
4 An infinite sequence of positive integers is called an "alph 20 16 Nov 2007, 17:22
Display posts from previous: Sort by