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# If y ≠ 3 and 3x/y is a prime integer greater than 2,

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VP
Joined: 09 Jul 2007
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Location: London
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If y ≠ 3 and 3x/y is a prime integer greater than 2, [#permalink]  22 Aug 2007, 15:32
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.
VP
Joined: 10 Jun 2007
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Re: prime intgr [#permalink]  22 Aug 2007, 19:44
Ravshonbek wrote:
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.

None.

3x/y = prime
x/y = prime/3
y and x doesn't need to equal.
Director
Joined: 03 May 2007
Posts: 894
Schools: University of Chicago, Wharton School
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Re: prime intgr [#permalink]  22 Aug 2007, 19:54
bkk145 wrote:
Ravshonbek wrote:
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.

None.

3x/y = prime
x/y = prime/3
y and x doesn't need to equal.

i guessed x and y as intger but not that is not necessary.

if x = 10/3 and y = 2, 3x/y = 5.

we can change the value to get the prime integer value for 3x/y.
Manager
Joined: 18 Jun 2007
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1 it is
Manager
Joined: 03 Sep 2006
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I'm confused. I also got Ans. 1)
What is the OA?
Senior Manager
Joined: 03 Jun 2007
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Actually 1 and 2 can be true if x and y are not assumed as intergers. Y can be 1 and x can 17/3
Director
Joined: 31 Mar 2007
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3x/y

Obviously x=y

y!=3, so y has to divide x evenly since its an integer. but then x/y is an integer, and if so, then by definition 3x/y is not a prime. hence x/y == 1, as 3 is prime. so x=y.
VP
Joined: 09 Jul 2007
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Re: prime intgr [#permalink]  23 Aug 2007, 10:40
bkk145 wrote:
Ravshonbek wrote:
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.

None.

3x/y = prime
x/y = prime/3
y and x doesn't need to equal.

Can u explain it indetals plz
Senior Manager
Joined: 28 Jun 2007
Posts: 320
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Re: prime intgr [#permalink]  23 Aug 2007, 11:08
Ravshonbek wrote:
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.

I think most people here are assuming that x and y are integers. This is not a given.

1> x = y

Lets use some susbtitution:

If 3x/y = 3 then x = y [x=4, y=4]
If 3x/y = 5 then x = 5/3y [x=5/3, y=1]

This shows that x = y is not necessarily true.

2> y = 1

This will mean 3x/y = 3x. 3x cannot be a prime number. Hence this is not true either.

3> x and y prime

If 3x/y is prime and greater than 2 then it is not necessary for x and y to be prime. Try a few numbers:

x = 5/3, y = 1
x = 14/3, y = 2
Director
Joined: 31 Mar 2007
Posts: 586
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Ah reals

Ok, none then
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