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

 It is currently 17 Oct 2019, 13:37 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  If √k is not an integer, then is k a prime number?

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

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58402
If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags 00:00

Difficulty:   45% (medium)

Question Stats: 52% (01:02) correct 48% (01:04) wrong based on 84 sessions

HideShow timer Statistics

If √k is not an integer, then is k a prime number?

(1) k < 10

(2) k < 5

_________________
NUS School Moderator V
Joined: 18 Jul 2018
Posts: 1020
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

1
From statement 1: If we take K as 8 then $$\sqrt{k}$$ = 2$$\sqrt{2}$$. Not an integer. But, 8 is not prime. If we take 7 then $$\sqrt{k}$$ is not an integer. But k is prime. Hence 1 is Insufficient.
From statement 2: If we take K as 2, 3 or 5. $$\sqrt{k}$$ is not an integer. And all the values of K are prime. Hence, B is sufficient.
_________________
Press +1 Kudos If my post helps!
VP  D
Status: Learning stage
Joined: 01 Oct 2017
Posts: 1014
WE: Supply Chain Management (Energy and Utilities)
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

Bunuel wrote:
If √k is not an integer, then is k a prime number?

(1) k < 10

(2) k < 5

Given, √k is not an integer, implies k is not a perfect square.

Question stem:- Is k a prime number?

St1:- k < 10

Possible values of k:- 1,2,3,4,5,6,7,8,9

k: 2,3,5,7 --> Prime
k: 6,8-----> Not prime.
Insufficient.

St2:- k < 5
Possible values of k:- 1,2,3,4
k: 2,3----> Prime
Sufficient.

Ans. (B)

P.S:- Here it is given that √k is not an integer. k is not necessarily an integer, it could be a positive rational number too.
In st2, k<5. Possible values of k could be any number between 0 to 5.

If I say k=0.5, √k is not an integer. hence, k is also not a prime number.

chetan2u, could you please clear my confusion. I know, an integer can be prime. I think it would be clear if the question stem mentions k to be an integer.
_________________
Regards,

PKN

Rise above the storm, you will find the sunshine
Math Expert V
Joined: 02 Aug 2009
Posts: 7971
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

Bunuel wrote:
If √k is not an integer, then is k a prime number?

(1) k < 10

(2) k < 5

Hi PKN

We have to read the question as it is and therefore answer should be E..

Since k can be 1.4, then it is NOT prime
If k is 3, it is Prime..
So insufficient

Answer would be B if it was given as an integer but that may be the catch
_________________
VP  D
Status: Learning stage
Joined: 01 Oct 2017
Posts: 1014
WE: Supply Chain Management (Energy and Utilities)
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

chetan2u wrote:
Bunuel wrote:
If √k is not an integer, then is k a prime number?

(1) k < 10

(2) k < 5

Hi PKN

We have to read the question as it is and therefore answer should be E..

Since k can be 1.4, then it is NOT prime
If k is 3, it is Prime..
So insufficient

Answer would be B if it was given as an integer but that may be the catch

Thank you Sir,
I am happy that my understanding is correct. i was biased a bit. I will keep my post as it is.
_________________
Regards,

PKN

Rise above the storm, you will find the sunshine
Manager  S
Joined: 20 Jul 2018
Posts: 87
GPA: 2.87
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

can 'k' take negative values as its not mentioned in the statement whether its positive or negative?
in that case answer would be 'E'.
k can also take fractional values so 'E' would be answer in that case as well
plz clarify
_________________
Hasnain Afzal

"When you wanna succeed as bad as you wanna breathe, then you will be successful." -Eric Thomas
VP  D
Status: Learning stage
Joined: 01 Oct 2017
Posts: 1014
WE: Supply Chain Management (Energy and Utilities)
Re: If √k is not an integer, then is k a prime number?  [#permalink]

Show Tags

hasnain3047 wrote:
can 'k' take negative values as its not mentioned in the statement whether its positive or negative?
in that case answer would be 'E'.
k can also take fractional values so 'E' would be answer in that case as well
plz clarify

Yes. You are absolutely correct. E must be the answer.
_________________
Regards,

PKN

Rise above the storm, you will find the sunshine Re: If √k is not an integer, then is k a prime number?   [#permalink] 13 Aug 2018, 10:16
Display posts from previous: Sort by

If √k is not an integer, then is k a prime number?

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

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