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If xy + x is a prime number, is xy + x a multiple of 3?
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02 Oct 2017, 00:28
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37% (02:21) correct 63% (02:24) wrong based on 131 sessions
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Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2
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If xy + x is a prime number, is xy + x a multiple of 3?
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02 Oct 2017, 04:10
Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 as \(xy+x\) is a prime no, so \(x\) cannot be \(0\) and only prime that is a multiple of \(3\) is \(3\) itself so the question is asking is \(xy+x=3\) Statement 1: \(xy=3\), add \(x\) to both sides, \(xy+x=3+x\) as explained earlier \(x\) is not equal to \(0\) so \(3+x\) cannot be equal to \(3\), hence \(xy+x\) is not a multiple of \(3\). SufficientStatement 2: substitute the value of \(x\) in question stem to get \(2y+2\) Now if \(y=\frac{1}{2}\), then \(xy+x=3\) and if \(y=\frac{3}{2}\), then \(xy+x=5\). Hence no unique answer. InsufficientOption A



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If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 02:56
Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 BunuelIs the question correct? or is there any typo? Statement 1: xy = 3 Let x =1 & y = 3...........xy+x = 3+1= NOT Prime ........condition highlighted failed. Let x =3 & y = 1...........xy+x = 3+3 = NOT Prime ........condition highlighted failed. Let x =3/2 & y = 2...........xy+x = 3 +3/2= NOT Prime ........condition highlighted failed. Let x =3 & y = 3/2...........xy+x = 3/2+2 = NOT Prime ........condition highlighted failed. Can you elaborate please????



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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:14
Mo2men wrote: Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 BunuelIs the question correct? or is there any typo? Statement 1: xy = 3 Let x =1 & y = 3...........xy+x = 3+1= NOT Prime ........condition highlighted failed. Let x =3 & y = 1...........xy+x = 3+3 = NOT Prime ........condition highlighted failed. Let x =3/2 & y = 2...........xy+x = 3 +3/2= NOT Prime ........condition highlighted failed. Let x =3 & y = 3/2...........xy+x = 3/2+2 = NOT Prime ........condition highlighted failed. Can you elaborate please???? Hi Mo2menuse x=2 & y=1/2 then you will get xy+x=3=Prime



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If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:17
niks18 wrote: Mo2men wrote: Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 BunuelIs the question correct? or is there any typo? Statement 1: xy = 3 Let x =1 & y = 3...........xy+x = 3+1= NOT Prime ........condition highlighted failed. Let x =3 & y = 1...........xy+x = 3+3 = NOT Prime ........condition highlighted failed. Let x =3/2 & y = 2...........xy+x = 3 +3/2= NOT Prime ........condition highlighted failed. Let x =3 & y = 3/2...........xy+x = 3/2+2 = NOT Prime ........condition highlighted failed. Can you elaborate please???? Hi Mo2menuse x=2 & y=1/2 then you will get xy+x=3=Prime Hi niks18, If I use your example above....then x * y does not equal 3 as per statement 1.



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If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:21
Quote: If I use your example above....then x * y does not equal 3 as per statement 1. Hi Mo2men(xy+x) is prime and not xy so if x=2 & y=1/2, then \(2*\frac{1}{2}+2 =1+2=3\)



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If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:26
niks18 wrote: Quote: If I use your example above....then x * y does not equal 3 as per statement 1. Hi Mo2men(xy+x) is prime and not xy so if x=2 & y=1/2, then \(2*\frac{1}{2}+2 =1+2=3\) Maybe I can't see something. Can you help me with statement 1 and come up with example that maintain both Statement 1 xy =3 & condition in the stem xy+x = Prime?



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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:30
Mo2men wrote: niks18 wrote: Quote: If I use your example above....then x * y does not equal 3 as per statement 1. Hi Mo2men(xy+x) is prime and not xy so if x=2 & y=1/2, then \(2*\frac{1}{2}+2 =1+2=3\) Maybe I can't see something. Can you help me with statement 1 and come up with example that maintain both Statement 1 xy =3 & condition in the stem xy+x = Prime? Hi Mo2menx=2 & y =3/2, then xy=2*3/2=3=Prime and xy+x=3+2=5=Prime



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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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03 Oct 2017, 03:39
niks18 wrote: Hi Mo2menx=2 & y =3/2, then xy=2*3/2=3=Prime and xy+x=3+2=5=Prime Hi niks18Thanks for bearing with me. I know where I got wrong. I totally missed up my 4th example when asked Bunuel. It seems my brain get burned after some study kudos to you



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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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24 Dec 2018, 02:57
Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 Par of GMAT CLUB'S New Year's Quantitative Challenge Set
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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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26 Dec 2018, 00:13
Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 Statement 1) xy=3, If xy+x is a prime number, then 3+x is a prime number and for it to be divisible by 3, x has to be zero because all other prime numbers greater than 3 are not divisible by 3. But x can't be 0 as xy=3. So, xy+x isn't divisible by 3. Sufficient. Statement 2) x=2. For y=1/2, xy+x=3, divisible by 3. For y=3/2, xy+x=5, not divisible by 3. Insufficient. Hence, Option A is correct.



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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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26 Dec 2018, 21:46
If xy+x is a prime no. as given in question then we already know that it is not multiple of any other than 1 and itself. We don't even need any of the two statements to say that. Then why isn't the answer 'D'?
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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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26 Dec 2018, 22:11
UdayPratapSingh wrote: If xy+x is a prime no. as given in question then we already know that it is not multiple of any other than 1 and itself. We don't even need any of the two statements to say that. Then why isn't the answer 'D'?
Posted from my mobile device xy+x is a prime number and is it a multiple of 3? so, as it is a prime number, x(y+1) is a prime number Now as 3 is a prime number, any prime number which is a multiple of 3 has to be 3. Now x(y+1) = 3, so X cant be Zero....this is important! A: xy = 3 and X is not 0, so Xy+ x is not a multiple of 3...............Sufficient B: x=2 now substitute x= 2, and y as 1 we get xy+y = 3 ........a multiple of 3 x= 2, and y as 1/2 we get xy+y = 5..........NOT a multiple of 3..........Statement 2 ALONE is insufficient
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Re: If xy + x is a prime number, is xy + x a multiple of 3?
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08 Oct 2019, 04:46
Bunuel wrote: Fresh GMAT Club Tests' Challenge Question: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 (2) x = 2 Asked: If xy + x is a prime number, is xy + x a multiple of 3? (1) xy = 3 Since xy+x is a prime number; xy is an integer; x is an integer x = {0,2,4,8,10.....} If x = 0; xy + x = 0 is NOT a prime number For all other values of x; xy+x is NOT a multiple of 3 SUFFICIENT (2) x = 2 2(y+1) is a prime number y={0,.5,1.5,...} For y = .5; xy+x is a multiple of 3 for all other values of y, xy+x is NOT a multiple of 3 NOT SUFFICIENT IMO A




Re: If xy + x is a prime number, is xy + x a multiple of 3?
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