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Prime numbers

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Prime numbers

by muna_m » Wed Jul 29, 2009 11:11 am
If y ≠ 3 and 2x/y is a prime integer greater than 2, which of the following must be true?
I. x = y
II. y = 1
III. x and y are prime integers.

(A) None

(B) I only

(C) II only

(D) III only

(E) I and II
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by ssmiles08 » Wed Jul 29, 2009 1:44 pm
I plugged in values for the problem.

x/y = 5/2

I) x is not equal to y

II) y is not 1

For III)

x/y can also be 6/4 in which case 2*(6/4) = 3

x and y are not primes.

IMO A.
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by pradeepsarathy » Wed Jul 29, 2009 5:23 pm
Statement I:
if x=y, then the expression 2x/y = 2.But, according to the question stem, the expression 2x/y is greater than 2.So I is not possible.

Statement II:
If y=1, then the expression is a multiple of 2.But, according to the question stem, the expression is a prime.Since none of the multiple of 2 is prime, statement II is also not possible

Statement III:
If x and y are prime integers, the expression 2x/y may be or may not be a prime, greater than 2.Hence statement III is also not possible.

IMO A
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