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# Is a product of three integers XYZ a prime? (1) X=-Y (2) Z=1

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Joined: 05 Jul 2006
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Is a product of three integers XYZ a prime? (1) X=-Y (2) Z=1 [#permalink]  10 Aug 2009, 09:59
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100% (00:00) correct 0% (00:00) wrong based on 3 sessions
Is a product of three integers XYZ a prime?

(1) X=-Y
(2) Z=1
Intern
Joined: 21 Jul 2009
Posts: 21
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: Primes [#permalink]  10 Aug 2009, 11:16
E for me.

1) X = -Y. therefore, XYZ = -X^2 Z. Not sure abt the value of Z, so Insuff
2) Z = 1. Insuff

Comb both, -X^2 , square of a number if never prime e.g. 2^2 = 4 has 1,2,4 as factors
Intern
Joined: 10 Jul 2009
Posts: 47
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Kudos [?]: 10 [0], given: 4

Re: Primes [#permalink]  10 Aug 2009, 21:33
yezz wrote:
Is a product of three integers XYZ a prime?

(1) X=-Y
(2) Z=1

C for me
For XYZ to be prime we need to have a positive product so values could be:
1)1*1*(any prime)
2)1*(-1)*-(any prime)
3) -1*-1*any prime

St 1 tells us that either X or Y is +ve, so we know that XY is -ve. We know nothing about Z. Please note that negative numbers cannot be primes, but there is still a possibility for the variant 2.

St 2 tells us Z=1. we know nothing about X and Y

Combining two statements together we can answer the question:
If X is any number we get a negative product of XYZ, and we know that no prime number can be negative. So answer is NO, thus SUFF
Re: Primes   [#permalink] 10 Aug 2009, 21:33
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