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Prime numbers

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by sivaelectric » Mon Jun 06, 2011 3:38 am
If X and Y are different prime numbers each greater than 2, which of the following must be true?

1. X + Y not equal to 73
2. XY is an odd integer
3. X/Y is not an integer

A. 2 only
B. 1 and 2 only
C. 1 and 3 only
D. 2 and 3 only
E. 1, 2 and 3
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by Vish_ » Mon Jun 06, 2011 3:42 am
IMO[spoiler] E[/spoiler]
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by sunilramu » Mon Jun 06, 2011 4:19 am
1. X + Y not equal to 73 - True as X and Y should both be odd and sum should be even.
2. XY is an odd integer - True as X and Y are both odd and product should be odd
3. X/Y is not an integer - True as X and Y are different and are primes.

IMO E
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by galaxian » Mon Jun 06, 2011 4:21 am
It should be E

As except 2 all prime nos are Odd.
hence,
1. odd + odd = has to be even, can never be 91
2. odd*odd = odd
3. prime no/ prime no can never be a whole integer.
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by sivaelectric » Mon Jun 06, 2011 4:24 am
Hey Galaxian, I have mentioned 73 and not 91. Where did that number come from? :)
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by galaxian » Mon Jun 06, 2011 4:30 am
Lol
I found a similar Qs here :
https://www.urch.com/forums/gmat-problem ... mbers.html

But am sure,given the difficulty level of this problem, you dont think I got the ans from here, do you ? :)
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by MBA.Aspirant » Mon Jun 06, 2011 5:47 am
nice question
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by cans » Mon Jun 06, 2011 6:36 am
If X and Y are different prime numbers each greater than 2, which of the following must be true?

1. X + Y not equal to 73
2. XY is an odd integer
3. X/Y is not an integer
X,Y odd prime numbers.
thus X+Y will be even (odd+odd=even) Thus 1 will always be true.
X is odd and Y is odd. Thus XY is odd. 2 will be always true.
X/Y are prime and are different. Thus not an integer. True
thus all 1,2,3 all are true
IMO E
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by sivaelectric » Mon Jun 06, 2011 8:00 am
@Galaxian Defn No. ;) lol
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by jainnikhil02 » Mon Jun 06, 2011 8:47 am
IMO E
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by Tani » Mon Jun 06, 2011 9:45 am
Given the restrictions that X and Y are different primes greater than 2, you could put any odd number in the place of 73 and get the same answer.
Tani Wolff
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