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

It is currently 16 Aug 2018, 05:09

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

is y prime number?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
B
Joined: 31 May 2018
Posts: 17
Location: United States
Concentration: Finance, Marketing
is y prime number?  [#permalink]

Show Tags

New post 26 Jul 2018, 23:52
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

50% (00:52) correct 50% (00:19) wrong based on 4 sessions

HideShow timer Statistics

is y prime number?

1) \(y^2\) has exactly 3 factors.
2) y is of form 6q+1
RC Moderator
User avatar
G
Status: Perfecting myself for GMAT
Joined: 22 May 2017
Posts: 420
Concentration: Nonprofit
Schools: Haas '21
GPA: 4
WE: Engineering (Computer Software)
GMAT ToolKit User Premium Member CAT Tests
Re: is y prime number?  [#permalink]

Show Tags

New post 27 Jul 2018, 00:00
To determine whether y is a prime number

Statement 1

\(y^2\) has exactly 3 factors

=> y * y has exactly 3 factors

=> the factors are 1, y and \(y^2\)

=> y must be a prime number because if y is not prime then there exist a factor other that 1 and y. Lets call it x

=> x must be a factor of \(y^2\) contradicting the given information that \(y^2\) has only 3 factors

=> y doesn't have any factor x such that 1 < x < y

=> y is a prime number

Statement 2

y is of the form 6q + 1

=> y = 6(2) + 1 = 13 a prime number

=> y = 6(4) + 1 = 25 not a prime number

Statement 2 is insufficient

Hence option A
_________________

If you like my post press kudos +1

New - RC Butler - 2 RC's everyday

Tag me in RC questions if you need help. Please provide your analysis of the question in the post along with the tag.

Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 6525
Re: is y prime number?  [#permalink]

Show Tags

New post 27 Jul 2018, 00:02
1
is y prime number?

1) \(y^2\) has exactly 3 factors.
number of factors of \(y^2\) is \((2+1)=3\)
possible only when y is prime...
for knowledge the factors are 1, y and y^2
suff

2) y is of form 6q+1
all prime numbers are of the form \(6K+1\) or \(6K-1\)
but vice versa may not be true..
\(k=1, 6*1+1=7...\) prime
\(k=4, 6*4+1=25...\) not a prime
insuff

A
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Re: is y prime number? &nbs [#permalink] 27 Jul 2018, 00:02
Display posts from previous: Sort by

is y prime number?

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

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.