If x and y are prime numbers, is y(x-3) odd ?
1) x > 10
2) y < 3
My workout -
x can be 11 ,13 ,17 ,19 and so on forth
lets say x is 11
Y ( 11-3) = y (8) , it can't be odd since it is multiplying with 8
2 ) y < 3
y =2
HELP !
Yelp (2)
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- candygal79
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Hi candygal79,
This DS question is built on Number Properties.
We're told that X and Y are PRIME numbers. We're asked if "Y(X-3) is odd?" This is a YES/NO question.
Here are the Number Properties worth knowing for this question:
Odd x Odd = Odd
Even x Odd = Even
Even x Even = Even
Fact 1: X > 10
Since X is PRIME and X > 10, this means that X MUST be ODD. Furthermore, this means that (X-3) MUST be EVEN. Notice that ANY integer multiplied by an EVEN yields an EVEN? So Y(X-3) will NEVER be ODD. This is CONSISTENT.
Fact 1 is SUFFICIENT
Fact 2: Y < 3
Since Y is PRIME, it Y MUST be 2. Here, we're dealing with the SAME Number Property rule as in Fact 1: Since Y is 2, 2(X-3) MUST be EVEN, so it will NEVER be odd. This is CONSISTENT.
Fact 2 is SUFFICIENT
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
This DS question is built on Number Properties.
We're told that X and Y are PRIME numbers. We're asked if "Y(X-3) is odd?" This is a YES/NO question.
Here are the Number Properties worth knowing for this question:
Odd x Odd = Odd
Even x Odd = Even
Even x Even = Even
Fact 1: X > 10
Since X is PRIME and X > 10, this means that X MUST be ODD. Furthermore, this means that (X-3) MUST be EVEN. Notice that ANY integer multiplied by an EVEN yields an EVEN? So Y(X-3) will NEVER be ODD. This is CONSISTENT.
Fact 1 is SUFFICIENT
Fact 2: Y < 3
Since Y is PRIME, it Y MUST be 2. Here, we're dealing with the SAME Number Property rule as in Fact 1: Since Y is 2, 2(X-3) MUST be EVEN, so it will NEVER be odd. This is CONSISTENT.
Fact 2 is SUFFICIENT
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
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- Brent@GMATPrepNow
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Rich's solution is great, so I won't say anything more about that.
I will say that GMAT questions featuring PRIME numbers are often testing your ability to recognize that not all prime numbers are odd.
There are many people who assume that 2 is not prime since it's even. However, an integer is prime if it has exactly 2 positive divisors. The positive divisors of 2 are 1 and 2, so 2 must, indeed, be prime. So, in reality, all prime numbers are odd with the exception of 2, which is even.
Cheers,
Brent
I will say that GMAT questions featuring PRIME numbers are often testing your ability to recognize that not all prime numbers are odd.
There are many people who assume that 2 is not prime since it's even. However, an integer is prime if it has exactly 2 positive divisors. The positive divisors of 2 are 1 and 2, so 2 must, indeed, be prime. So, in reality, all prime numbers are odd with the exception of 2, which is even.
Cheers,
Brent
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Hi All ,
Statement 2 says that y<3 .
so y can be negative also like (-2,-5......)
Please advise.
Thanks
Shreyans
Statement 2 says that y<3 .
so y can be negative also like (-2,-5......)
Please advise.
Thanks
Shreyans
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The prompt states that x and y are PRIME.j_shreyans wrote:Hi All ,
Statement 2 says that y<3 .
so y can be negative also like (-2,-5......)
Please advise.
Thanks
Shreyans
The smallest prime number is 2.
No negative integers are prime.
In statement 2, y must be a prime number less than 3.
Since 2 is the only prime number less than 3, statement 2 implies that y=2.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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