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Senior Manager
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If x is a prime number, what is the value of x? (1) 2x + 2 [#permalink]
 25 Jun 2007, 19:26
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If x is a prime number, what is the value of x?
(1) 2x + 2 is the cube of a positive integer.
(2) The average of any x consecutive integers is an integer.
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Director
Joined: 13 Mar 2007
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Schools: MIT Sloan
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A?
St1 - can think of x=3
St2 - true for any odd value of x
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Senior Manager
Joined: 27 Jul 2006
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ST. 1
I never know how to go about primes. I have noticed that the cubes tend to be 64 and 27
I check these numbers and see that they both work
insufficient.
Statement 2
every prime will have an average of an integer since it is odd.
average will be the mean in this case. if the number is 13 the average will be the 7th integer, 17 the 8th integer and so on.
insufficient.
together. I pointed out that 13 and and 31 both work here, and their averages are 7 and 16 respectively, also insuff.
Therefore E
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Senior Manager
Joined: 21 Jun 2006
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A is not sufficient
2x+2 = 6
x=3 gives 8 which is cube of 3
x=31 gives 64 which is cube of 4
B is also not sufficient as it can mean that x is any odd number.
E
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