GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 13 Dec 2019, 03:09

Close

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
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.

Close

Request Expert Reply

Confirm Cancel

An infinite sequence of positive integers is called a coprime sequence

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Senior Manager
Senior Manager
avatar
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 439
Location: United Kingdom
Concentration: International Business, Strategy
GMAT 1: 730 Q49 V45
GPA: 2.9
WE: Information Technology (Consulting)
An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 13 Feb 2012, 17:14
8
27
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

49% (01:08) correct 51% (01:08) wrong based on 488 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?

_________________
Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59722
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 13 Feb 2012, 19:07
6
3
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.
_________________
General Discussion
Manager
Manager
avatar
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

New post 06 Jun 2012, 19:33
1
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
Manager
User avatar
Affiliations: Project Management Professional (PMP)
Joined: 30 Jun 2011
Posts: 122
Location: New Delhi, India
Re: coprime  [#permalink]

Show Tags

New post 06 Jun 2012, 20:22
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
Manager
avatar
Joined: 25 Oct 2013
Posts: 141
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 08 Feb 2014, 04:38
1
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
Manager
avatar
Joined: 28 Jul 2013
Posts: 62
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

New post 16 Apr 2015, 18:53
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
User avatar
V
Joined: 16 Oct 2010
Posts: 9876
Location: Pune, India
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 17 Apr 2015, 01:49
1
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
Manager
avatar
Joined: 28 Jul 2013
Posts: 62
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

New post 17 Apr 2015, 01:57
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
User avatar
V
Joined: 16 Oct 2010
Posts: 9876
Location: Pune, India
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 17 Apr 2015, 02:03
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
Director
User avatar
B
Status: I don't stop when I'm Tired,I stop when I'm done
Joined: 11 May 2014
Posts: 522
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

New post 09 Jun 2016, 16:12
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
Senior Manager
avatar
S
Joined: 15 Jan 2017
Posts: 332
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 02 Oct 2017, 12:48
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
Intern
avatar
B
Joined: 07 Sep 2019
Posts: 38
Re: An infinite sequence of positive integers is called a coprime sequence  [#permalink]

Show Tags

New post 26 Nov 2019, 11:03
thinkvision - Check this out!
GMAT Club Bot
Re: An infinite sequence of positive integers is called a coprime sequence   [#permalink] 26 Nov 2019, 11:03
Display posts from previous: Sort by

An infinite sequence of positive integers is called a coprime sequence

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





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