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Is x a prime number?

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Is x a prime number?  [#permalink]

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New post 27 Mar 2019, 03:15
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

10% (00:14) correct 90% (01:28) wrong based on 10 sessions

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Is x a prime number?

1. xyz has only 8 distinct factors.

2. xy is even when y is a prime number.




Source : Barron's GMAT

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Re: Is x a prime number?  [#permalink]

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New post 27 Mar 2019, 05:58
Pls explain how it is A

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Re: Is x a prime number?  [#permalink]

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New post 27 Mar 2019, 06:53
Top Contributor
AkshdeepS wrote:
Is x a prime number?

1. xyz has only 8 distinct factors.

2. xy is even when y is a prime number.


Target question: Is x a prime number?

Statement 1: xyz has only 8 distinct factors.
Let's TEST some values.
There are several values of x, y and z that satisfy statement 1. Here are two:
Case a: x = 3, y = 2 and z = 5 (xyz = 30, and 30 has 8 factors). In this case, the answer to the target question is YES, x IS prime
Case b: x = 1, y = 2 and z = 15. In this case, the answer to the target question is NO, x is NOT prime
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: xy is even when y is a prime number.
Let's TEST some values.
There are several values of x, y and z that satisfy statement 2. Here are two:
Case a: x = 3, y = 2 and z = 5. In this case, the answer to the target question is YES, x IS prime
Case b: x = 1, y = 2 and z = 15. In this case, the answer to the target question is NO, x is NOT prime
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
There are several values of x, y and z that satisfy BOTH statements. Here are two:
Case a: x = 3, y = 2 and z = 5. In this case, the answer to the target question is YES, x IS prime
Case b: x = 1, y = 2 and z = 15. In this case, the answer to the target question is NO, x is NOT prime
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

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Brent
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New post 27 Mar 2019, 08:36
Aderonke01 wrote:
Pls explain how it is A

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I need to cross check the OA. Inconvenience regreted...
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Re: Is x a prime number?  [#permalink]

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New post 27 Mar 2019, 23:25
AkshdeepS wrote:
Is x a prime number?

1. xyz has only 8 distinct factors.

2. xy is even when y is a prime number.




Source : Barron's GMAT


Though OA given is A, but I think question is flawed.

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Re: Is x a prime number?   [#permalink] 27 Mar 2019, 23:25
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