If x and y are positive integers, is x a prime number?
(1) |x−2|<2−y.
(2) x+y−3=|1−y|.
is x a prime number?
This topic has expert replies
GMAT/MBA Expert
- [email protected]
- Elite Legendary Member
- Posts: 10392
- Joined: Sun Jun 23, 2013 6:38 pm
- Location: Palo Alto, CA
- Thanked: 2867 times
- Followed by:511 members
- GMAT Score:800
Hi himu,
This DS question is perfect for the Empowergmat tactic TEST IT.
We're told that x and y are POSITIVE INTEGERS. The prompt asks "Is x prime?" This is a Yes/No question.
Fact 1 gives us |x - 2| < 2 - y
There's an interesting number property here because the left hand side can never be less than 0 and the right hand side can be no greater than 1
If y = 1, then x = 2 The answer is YES, but....
There's only one possible value for x. By definition, that is SUFFICIENT.
Fact 2 gives us x + y - 3 = |1 - y|
If y = 1, then x = 2 The answer is YES
If y = 2, then x = 1 The answer is NO
Inconsistent = INSUFFICIENT
Final Answer: A (1 only is SUFFICIENT
GMAT assassins aren't born, they're made,
Rich
This DS question is perfect for the Empowergmat tactic TEST IT.
We're told that x and y are POSITIVE INTEGERS. The prompt asks "Is x prime?" This is a Yes/No question.
Fact 1 gives us |x - 2| < 2 - y
There's an interesting number property here because the left hand side can never be less than 0 and the right hand side can be no greater than 1
If y = 1, then x = 2 The answer is YES, but....
There's only one possible value for x. By definition, that is SUFFICIENT.
Fact 2 gives us x + y - 3 = |1 - y|
If y = 1, then x = 2 The answer is YES
If y = 2, then x = 1 The answer is NO
Inconsistent = INSUFFICIENT
Final Answer: A (1 only is SUFFICIENT
GMAT assassins aren't born, they're made,
Rich
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
I may be missing something here, but the second statement looks sufficient.
Assuming x and y are positive integers, the second statement gives us
x + y - 3 = (y - 1)
since for all y greater than or equal to 1, |1 - y| = (y - 1).
Adding 3 to both sides, we have x + y = y + 2, or x = 2, so x is a prime number.
Rich, I think your numbers are off in your explanation - if y = 2, x = 2.
Assuming x and y are positive integers, the second statement gives us
x + y - 3 = (y - 1)
since for all y greater than or equal to 1, |1 - y| = (y - 1).
Adding 3 to both sides, we have x + y = y + 2, or x = 2, so x is a prime number.
Rich, I think your numbers are off in your explanation - if y = 2, x = 2.