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sandeep1306: Senior | Next Rank: 100 Posts; Posts: 39; Joined: Wed Jan 19, 2011 7:57 am; Location: bangalore

by sandeep1306 » Sun Jun 19, 2011 7:44 pm

If x and y are positive integers and 3x + 5 < x + 11, is x a prime number?

(1) The sum of x and y is even.

(2) The product of x and y is odd.

OA is B

Thanks,
Sandeep

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Source: Beat The GMAT — Data Sufficiency | Sun Jun 19, 2011 7:44 pm

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Sun Jun 19, 2011 8:06 pm

Hi,
3x+5 < x+11
So, 2x < 6 => x<3
As x and y are positive integers, x=1 or 2
From(1):
sum of x and y is even.
if y is odd, x=1
if y is even, x=2
Not sufficient
From(2):
product of x and y is odd. So, x and y are both odd.
So, x=1 which is not prime
Sufficient

Hence, B

Cheers!

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amit2k9: Master | Next Rank: 500 Posts; Posts: 461; Joined: Tue May 10, 2011 9:09 amFollowed by: 3 members; Location: pune; Thanked: 36 times

by amit2k9 » Sun Jun 19, 2011 10:45 pm

x<3 means x can be either 1 or 2.

a y can be 3,5 or 4,6 with x 1,2. not sufficient.

b x cannot be 2. thus B it is.

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