Author 
Message 
TAGS:

Hide Tags

Senior Manager
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 439
Location: United Kingdom
Concentration: International Business, Strategy
GPA: 2.9
WE: Information Technology (Consulting)

An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
13 Feb 2012, 16:14
Question Stats:
48% (01:08) correct 52% (01:08) wrong based on 508 sessions
HideShow timer Statistics
An infinite 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 infinite 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. 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?
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Best Regards, E.
MGMAT 1 > 530 MGMAT 2> 640 MGMAT 3 > 610 GMAT ==> 730




Math Expert
Joined: 02 Sep 2009
Posts: 61385

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
13 Feb 2012, 18:07
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. Answer: B.
_________________




Manager
Joined: 22 Apr 2011
Posts: 112
Schools: Mccombs business school, Mays business school, Rotman Business School,

An infinite sequence of positive integers is called a
[#permalink]
Show Tags
06 Jun 2012, 18:33
An infinite 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 infinite sequence of distinct positive integers, is S a coprime sequence?
(1) An in
finite number of integers in S are prime. (2) Each term in S has exactly two factors.
does the statement 1 mean that all numbers in sequence S are prime???



Manager
Affiliations: Project Management Professional (PMP)
Joined: 30 Jun 2011
Posts: 118
Location: New Delhi, India

Re: coprime
[#permalink]
Show Tags
06 Jun 2012, 19:22
alchemist009 wrote: An infinite 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 inf
inite sequence of distinct positive integers, is S a coprime sequence? (1) An in
finite number of integers in S are prime. (2) Each term in S has exactly two factors.
does the statement 1 mean that all numbers in sequence S are prime??? IMO answer is "B" we have to determine if all the integers in series are prime or not stm 1: it says number of integers is prime so the series can contain prime numbers or not hence : NOT SUFFICIENT Stm 2: Each number is a prime number : Hence SUFFICIENT



Manager
Joined: 25 Oct 2013
Posts: 138

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
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!



Manager
Joined: 28 Jul 2013
Posts: 61
Location: India
Concentration: Marketing, Strategy
GPA: 3.62
WE: Engineering (Manufacturing)

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
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: 10113
Location: Pune, India

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
17 Apr 2015, 00:49
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
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Manager
Joined: 28 Jul 2013
Posts: 61
Location: India
Concentration: Marketing, Strategy
GPA: 3.62
WE: Engineering (Manufacturing)

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
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: 10113
Location: Pune, India

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
17 Apr 2015, 01:03
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
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Director
Status: I don't stop when I'm Tired,I stop when I'm done
Joined: 11 May 2014
Posts: 518
Location: Bangladesh
Concentration: Finance, Leadership
GPA: 2.81
WE: Business Development (Real Estate)

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
09 Jun 2016, 15:12
Bunuel wrote: 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.
Answer: B. Great analysis. Can you just provide similar tricky(referred to Statement 1 type trap) question to practice? Thanks



Senior Manager
Joined: 15 Jan 2017
Posts: 319

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
02 Oct 2017, 11:48
A) An infinite number of integers in S are prime. ^ would mean; what about the other integers? there maybe infinite PRIME integers in S but what about non prime?So NS B)Each term in S has exactly two factors. Only a prime has ITSELF and one as their factors.
B is Sufficient



Intern
Joined: 07 Sep 2019
Posts: 40

Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
Show Tags
26 Nov 2019, 10:03
thinkvision  Check this out!




Re: An infinite sequence of positive integers is called a coprime sequence
[#permalink]
26 Nov 2019, 10:03






