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

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SVP
Joined: 03 Feb 2003
Posts: 1608
Followers: 6

Kudos [?]: 76 [0], given: 0

Is a product of three integers XYZ a prime? (1) X=Y (2) Z=1 [#permalink]  19 Jun 2003, 07:18
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Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 2 sessions
Is a product of three integers XYZ a prime?

(1) X=–Y
(2) Z=1
Manager
Joined: 03 Jun 2003
Posts: 84
Location: Uruguay
Followers: 1

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

C?

From 1, maybe or maybe not
From 2, nothing

Together, you now it is impossible to get a prime
Manager
Joined: 12 Mar 2003
Posts: 59
Followers: 1

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

Ans : C

1) Z could be -ve thus => insuff
2) X*Y could be prime => insuff

Combined :

X*Y*Z = -ve number

and since X=-Y, X*X can never be prime

Ans NO => Suff
SVP
Joined: 03 Feb 2003
Posts: 1608
Followers: 6

Kudos [?]: 76 [0], given: 0

tzolkin wrote:
Ans : C

1) Z could be -ve thus => insuff
2) X*Y could be prime => insuff

Combined :

X*Y*Z = -ve number

and since X=-Y, X*X can never be prime

Ans NO => Suff

You move in the right direction, either set is not sufficient. Combine -- the product is –X^2, a negative number can NEVER be a prime! If X=0, then tha product is 0, which is not prime either. Thus, C.
Current Student
Joined: 28 Dec 2004
Posts: 3391
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 181 [0], given: 2

I would say this has to be B...

x*y*z=prime?

1) x=-y, lets see if x=2, then y=-2 x*y=-4*if z=-1 then product not a prime..suppose x=-1 y=1 then -1*z if z=-3 then product is 3 (prime) Insuff

2) z=1, taking above example.....

1*-2*2=-4 not a prime..you can try other numbers...it will always never be a prime..B has to be it...

I wish styolar was around..to verify.but i think B is the right
VP
Joined: 22 Oct 2006
Posts: 1443
Schools: Chicago Booth '11
Followers: 8

Kudos [?]: 154 [0], given: 12

fresinha12 wrote:
I would say this has to be B...

x*y*z=prime?

1) x=-y, lets see if x=2, then y=-2 x*y=-4*if z=-1 then product not a prime..suppose x=-1 y=1 then -1*z if z=-3 then product is 3 (prime) Insuff

2) z=1, taking above example.....

1*-2*2=-4 not a prime..you can try other numbers...it will always never be a prime..B has to be it...

I wish styolar was around..to verify.but i think B is the right

B is insuff

because 1 * 1 * 1 Not Prime
2 * 1 * 1 Prime
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