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If y ≠ 3 and 3x/y is a prime integer greater than 2, which [#permalink]
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01 Apr 2009, 02:27
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If y ≠ 3 and 3x/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 III == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.
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Re: Number property........... [#permalink]
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01 Apr 2009, 02:47
good Q Prime Integers are 2,3,5,7,11,13,............ IMO C See, 3x/y is a prime integer greater than 2 say 3 hence That prime integer(3) will have 2 divisors 3 and x/yhence x=y is it from OG 12?20. If y ≠ 3 and 3x/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) Ⅱonly (D) Ⅲonly (E) Ⅰand Ⅲ
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Re: Number property........... [#permalink]
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01 Apr 2009, 16:56
I got A. You can pick numbers that contradict all three statements. What is the OA? == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.



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Re: ps Number property........... [#permalink]
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02 Apr 2009, 15:44
A.
z=3x/y for z to be prime number x=10 y=6 I is not true
Y could be 1 where our question asks must be...
Prime number could be... with x/y 3/3, 15/15



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Re: ps Number property........... [#permalink]
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02 Apr 2009, 23:33
My answer is B.
3x/y = 3*(x/y) < prime number that is greater than 2. if x and y are equal than the eqn becomes 3 * (1) = 3 (prime number greater than 2)
Since we are looking for an integer (all prime numbers are integers) and y != 3 than x must equal y.



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Re: ps Number property........... [#permalink]
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03 Apr 2009, 17:14
matrix777 wrote: My answer is B.
3x/y = 3*(x/y) < prime number that is greater than 2. if x and y are equal than the eqn becomes 3 * (1) = 3 (prime number greater than 2)
Since we are looking for an integer (all prime numbers are integers) and y != 3 than x must equal y. Initially I fell for it but take x=14 and y =6 3x/y = 7 which is still a prime and x ! = y Hence B is not correct.



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Re: ps Number property........... [#permalink]
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06 Apr 2009, 17:42
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The answer is A  Other than picking numbers, is there any option here ? I spent more than 2 minutes on this and fell for the wrong answer. pradeep
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Re: ps Number property........... [#permalink]
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08 Apr 2009, 05:36
take x=10 and y=6 and hence the answer is A.



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Re: ps Number property........... [#permalink]
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07 May 2009, 21:22
Ans must be B
3x/y and if x=y then ans is 3 and 3 is prime number, which is greater than 2. so ans must be B. Please post OA.



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Re: PS Number property [#permalink]
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12 Oct 2009, 08:38
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(3x/y) is a prime integer greater than 2. which of the following must be true
Suppose P=3x/y
Possible values of P = 3,5,7,11 ......
Statement I: If P = 3 , x=y TRUE If P = 5, x=y FALSE <== Statement I is not always correct
Statement II: If y=1 is TRUE => P = 3x Since P is a prime number, it cannot be a multiple of 3
Statement III: suppose x = 7 and y=5 , P= 21/5 => Not a prime number You can fill some other values of x and y
Answer should be A



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Re: PS Number property [#permalink]
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12 Oct 2009, 11:49
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If y ≠ 3 and 3x/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 Ⅲ Answer to this question is A. None of the statements (I,II,III) must be true. This Q. can be solved by number plugging in a minute but it's quite tricky, so let's generalize it so to understand the concept, as there are many similar problems in GMAT: Q. says that: y≠3 and that 3x/y IS a prime integer. Then it asks which of the statements MUST be true? First note that it's not stated that x and y are integers or positive/negative. Generally, the expression 3x/y is always prime in two cases: When x is a multiple of prime and y is same multiple of three: x=pn and y=3n (p prime >2, n ANY number but 1), so we have 3(pn)/3n=p. AND When x=y ≠1 then 3x/y=3=p>2 Note that first formula also gives us the p=3 but only when x and y are the multiples of three (n ANY number but 1, can be 6 or 75 but not 1), thus it exclude all possibilities when x=y and ARE not multiples of three, for instance x=8 and y=8. So from above it's not necessary x=y or y=1 or x,y to be primes. Let's look: I. x = y > not necessarily true: x=25 y=15 3x/y=5 II. y=1 > not necessarily true: x=8 y=8 3x/y=3 III. x and y are prime integers > x=21 y=9 3x/y=7
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Re: PS Number property [#permalink]
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13 Oct 2009, 11:55
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I got A picking x=16 and y=6..we get 3x/y = 7....thus OA A
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Re: Number properties: [#permalink]
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07 Jun 2010, 04:23
I'm assuming that the question reads ... and x is a prime integer greater than 2.
In these questions, always start with III
III. x and y are prime integers. Well x is a prime integer. But y could be any number other than 3. NOT TRUE.
II. y = 1. Need not be true. y could be anything other than 3.
I. x = y. Need not be true. y could be anything other than 3.
Pick A
Rather basic question, doubt you'll see this in the actual test.



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Re: PS section 1 q20 [#permalink]
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08 Jun 2010, 12:28
sunland wrote: 20. If y ≠ 3 and 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) Ⅱonly (D) Ⅲonly (E) Ⅰand Ⅲ
the solution booklet says answer is A but shouldnt x=y making B the answer if the number is prime and greater than 2, then the number has to be 3. which is possible only if x=y. First of all the question misses important part (\(\frac{3x}{y}=prime\)). Second this question is MUST be true question not COULD be true. Refer to the solutions above to see that it's not necessary x=y to be true for 3x/y to be a prime integer greater than 2. For example \(x=25\) and \(y=15\) > \(\frac{3x}{y}=5=prime\). Hope it's clear.
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Re: PS Number property [#permalink]
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01 Aug 2011, 00:38
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Except for A, the rest I just need to determine the other two which one is prime number SMAbbas wrote: (3x/y) is a prime integer greater than 2. which of the following must be true
Suppose P=3x/y
Possible values of P = 3,5,7,11 ......
Statement I: If P = 3 , x=y TRUE If P = 5, x=y FALSE <== Statement I is not always correct
Statement II: If y=1 is TRUE => P = 3x Since P is a prime number, it cannot be a multiple of 3
Statement III: suppose x = 7 and y=5 , P= 21/5 => Not a prime number You can fill some other values of x and y
Answer should be A



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Re: If y ≠ 3 and 3x/y is a prime integer greater than 2, which [#permalink]
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03 Jan 2014, 07:11
Done by Plugging in y#3 and 3x/y = prime number > 2 ,so 3,5,7,11... 1. x = y , x,y = 2 answer is 3 ; x,y = 3 or 4 or 5... answer is 3 which is a prime number then why this option is wrong 2. y = 1 its straight away wrong 3. x,y both prime any prime numbers so wrong why 1 option is wrong?? but after seeing with other numbers and bunnel post i realized that even if x= 35 , y = 15 the prime number is 7 even though which is >2
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Re: Number properties: [#permalink]
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13 Jan 2014, 20:22
AbhayPrasanna wrote: I'm assuming that the question reads ... and x is a prime integer greater than 2.
In these questions, always start with III
III. x and y are prime integers. Well x is a prime integer. But y could be any number other than 3. NOT TRUE.
II. y = 1. Need not be true. y could be anything other than 3.
I. x = y. Need not be true. y could be anything other than 3.
Pick A
Rather basic question, doubt you'll see this in the actual test. Can you explain your reasoning to (I)?



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Re: Number properties: [#permalink]
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14 Jan 2014, 20:42
TooLong150 wrote: Can you explain your reasoning to (I)? If a prime number is written as a product of two numbers, one of them must be prime and the other must be 1. 3x/y would be prime if 'x/y is 1' (in which case 3x/y = 3) or '3 gets canceled off from a 3 in y and the leftover is a prime number' So some solutions are: x = y = 1 x = y = Anything other than 0 y is a multiple of 3, say 3n and x/n is a prime number. We are given that y is not 3 but we are not given that it is not a multiple of 3. Say, y = 6 = 3n. In that case x/n can be a prime number. e.g. x = 10 or 14 or 26 etc 3x/y = 3*10/6 = 5 3x/y = 3*14/6 = 7 etc So x = 14, y = 6 is a solution. So it not NECESSARY (but it is possible) that x=y, y = 1, x and y are prime Answer (A)
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Re: If y ≠ 3 and 3x/y is a prime integer greater than 2, which [#permalink]
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19 Apr 2014, 21:28
y !=3 x * (3/y) I. x = y x * 3/x > 2 3> 2 Hence Must be true for the inequality to hold II. y = 1 x * 3/1 > 2 Could be true if x=1 III. x and y are prime integers. Then the expression itself wont be an integer except when x=y Could be true Hence only (1) is must be true
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Re: If y ≠ 3 and 3x/y is a prime integer greater than 2, which [#permalink]
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21 Mar 2016, 18:16
I got A! 3x3x5/3x3 = 5  prime number x=15, y=9  so x=y  no. B and E out. y=1  above mentioned example  C out. x=15, y=9  D is out.




Re: If y ≠ 3 and 3x/y is a prime integer greater than 2, which
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