Last visit was: 23 May 2024, 06:28 It is currently 23 May 2024, 06:28
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
SORT BY:
Date
User avatar
Intern
Intern
Joined: 31 May 2010
Posts: 43
Own Kudos [?]: 198 [8]
Given Kudos: 25
Send PM
User avatar
Intern
Intern
Joined: 31 May 2010
Posts: 43
Own Kudos [?]: 198 [3]
Given Kudos: 25
Send PM
Math Expert
Joined: 02 Sep 2009
Posts: 93417
Own Kudos [?]: 626039 [2]
Given Kudos: 81940
Send PM
User avatar
Senior Manager
Senior Manager
Joined: 01 Feb 2011
Posts: 309
Own Kudos [?]: 324 [0]
Given Kudos: 42
Send PM
Re: Inequality - Prime number [#permalink]
Given 2x/y is prime >2

could be {3,5,7,11....}

I) x = y => 2x/y = 2 , 2 will never be prime >2 (Ruled out)
II)y=1 . Not necessarily. 2 (3)/2 = 3 which is prime and here y is 2 (Ruled out)
III)x and y are prime integers . not necessarily . (Ruled out)
2(3)/2 x and y prime
2(21)/6 x and y are not prime.

Answer is A (None)
User avatar
Manager
Manager
Joined: 08 Jan 2011
Status:==GMAT Ninja==
Posts: 149
Own Kudos [?]: 217 [0]
Given Kudos: 46
Schools:ISB, IIMA ,SP Jain , XLRI
 Q48  V24 GMAT 2: 610  Q48  V27
WE 1: Aditya Birla Group (sales)
WE 2: Saint Gobain Group (sales)
Send PM
Re: Inequality - Prime number [#permalink]
Bunuel wrote:
saurabhgoel wrote:
35. If y ≠ 3 and 2x/y is a prime integer greater than 2, which of the following must be true?
I. x = y
II. y = 1
III. x and y are prime integers.

(A) None

(B) I only

(C) II only

(D) III only

(E) I and II


I dont know the OA ? So please help ?
My pick is (A)


Note that we are asked "which of the following MUST be true, not COULD be true. For such kind of questions if you can prove that a statement is NOT true for one particular set of numbers, it will mean that this statement is not always true and hence not a correct answer.

So we should try to make the listed statements not true for some x and y (which satisfy y≠3 and 2x/y=prime>2).

I. x = y --> not necessarily true: x=3 and y=2 (2x/y=3=prime>2);

II. y=1 --> not necessarily true: x=3 and y=2 (2x/y=3=prime>2);

III. x and y are prime integers --> not necessarily true: x=10 and y=4 (2x/y=5=prime>2).

Answer: A.


Dear bunuel
can't we go have another approach
by considering the options from 1st to 3rd
and see if 2x/y is not a prime no >2
as below
I. x = y --> then 2x/y=2 which is not greater then 2 so can't be true
II. y=1 --> then 2x/y=2 which is also not greater then 2 so can't be true
III. x and y are prime integers --> then this value will be fractional only so cant be an INTEGER so can't be true

hence A is the answer

please enlighten me for this approach :)

Regards
Puneet
User avatar
Manager
Manager
Joined: 08 Jan 2011
Status:==GMAT Ninja==
Posts: 149
Own Kudos [?]: 217 [0]
Given Kudos: 46
Schools:ISB, IIMA ,SP Jain , XLRI
 Q48  V24 GMAT 2: 610  Q48  V27
WE 1: Aditya Birla Group (sales)
WE 2: Saint Gobain Group (sales)
Send PM
Re: Inequality - Prime number [#permalink]
Bunuel wrote:
saurabhgoel wrote:
35. If y ≠ 3 and 2x/y is a prime integer greater than 2, which of the following must be true?
I. x = y
II. y = 1
III. x and y are prime integers.

(A) None

(B) I only

(C) II only

(D) III only

(E) I and II


I dont know the OA ? So please help ?
My pick is (A)


Note that we are asked "which of the following MUST be true, not COULD be true. For such kind of questions if you can prove that a statement is NOT true for one particular set of numbers, it will mean that this statement is not always true and hence not a correct answer.

So we should try to make the listed statements not true for some x and y (which satisfy y≠3 and 2x/y=prime>2).

I. x = y --> not necessarily true: x=3 and y=2 (2x/y=3=prime>2);

II. y=1 --> not necessarily true: x=3 and y=2 (2x/y=3=prime>2);

III. x and y are prime integers --> not necessarily true: x=10 and y=4 (2x/y=5=prime>2).

Answer: A.



Dear bunuel
can't we go have another approach
by considering the options from 1st to 3rd
and see if 2x/y is not a prime no >2
as below
I. x = y --> then 2x/y=2 which is not greater then 2 so can't be true
II. y=1 --> then 2x/y=2x which is an even number always so can't be true
III. x and y are prime integers --> then this value will be fractional only so cant be an INTEGER so can't be true

hence A is the answer

please enlighten me for this approach :)

Regards
Puneet
User avatar
Intern
Intern
Joined: 03 Jan 2013
Posts: 46
Own Kudos [?]: 11 [1]
Given Kudos: 44
GPA: 3.8
WE:Engineering (Computer Software)
Send PM
If y ≠ 3 and 2x/y is a prime integer greater than 2, which of th [#permalink]
1
Kudos
'A' is the right option. Condition III is satisfied when y=2 and x= some prime integer, but for other primes, it negates the condition. Hence 'None'.
User avatar
Intern
Intern
Joined: 19 May 2012
Posts: 16
Own Kudos [?]: 14 [1]
Given Kudos: 0
Location: India
Concentration: International Business, Healthcare
GMAT Date: 03-03-2014
WE:Information Technology (Computer Software)
Send PM
Re: If y ≠ 3 and 2x/y is a prime integer greater than 2, which [#permalink]
1
Kudos
I think we can do it in a more simple way:
2x/y=prime
-->2x=prime * y ,that is, 2x=odd*odd which is never possible.
None of the options will satisfy dis...
Hence A.
Manager
Manager
Joined: 10 Mar 2013
Posts: 136
Own Kudos [?]: 495 [0]
Given Kudos: 2412
GMAT 1: 620 Q44 V31
GMAT 2: 610 Q47 V28
GMAT 3: 700 Q49 V36
GMAT 4: 690 Q48 V35
GMAT 5: 750 Q49 V42
GMAT 6: 730 Q50 V39
GPA: 3
Send PM
Re: If y ≠ 3 and 2x/y is a prime integer greater than 2, which [#permalink]
This question seems to be transcribed incorrectly. I think it should be either y != 2 and 2x/y = prime > 2 or y != 3 and 3x/y = prime > 2.
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 33151
Own Kudos [?]: 829 [0]
Given Kudos: 0
Send PM
Re: If y 3 and 2x/y is a prime integer greater than 2, which [#permalink]
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
Re: If y 3 and 2x/y is a prime integer greater than 2, which [#permalink]
Moderator:
Math Expert
93417 posts