I had the following DS question in my Gmatprep test. It's just confusing me as I don't think the answer is C.
The question says, x and y are integers, is x*(y+1) even ?
1- x and y are prime numbers
2 - x > 7
my answer was A, but Gmatprep said C
Did anybody encounter the same question ?
Thank you
A question from Gmat prep
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- jayhawk2001
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I can't see how the answer can be C.
1 - Insufficient. As an example,
x = 3, y = 2 implies x(y+1) is odd
x = 2, y = 3 implies x(y+1) is even
2 - Insufficient. x can be even or odd
Combining 1 and 2, we can infer that x is odd.
If y is 2, x(y+1) is odd
If y is 3,5,7 ... x(y+1) is even
So, I'm inclined towards E.
1 - Insufficient. As an example,
x = 3, y = 2 implies x(y+1) is odd
x = 2, y = 3 implies x(y+1) is even
2 - Insufficient. x can be even or odd
Combining 1 and 2, we can infer that x is odd.
If y is 2, x(y+1) is odd
If y is 3,5,7 ... x(y+1) is even
So, I'm inclined towards E.
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I did get this question when I took the practice test
Have u written "-x and y are prime numbers" and "-x>7"?
As far as I remember, the statements were "x and y are prime" and "x>7"
Moreover primes are always positive.
Have u written "-x and y are prime numbers" and "-x>7"?
As far as I remember, the statements were "x and y are prime" and "x>7"
Moreover primes are always positive.
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So if you consider the first statement
"x and y are prime"
x(y+1)
for x=2 and y=3 , 2*4=Even
for x=3 and y=2, 3*3=Odd
Hence, insufficient
Second Statement "x>7" is insufficient coz x can be even making the product even or x and y can both be odd making the product odd.
Together Also
x=11,13....
y=2,3,5 etc
Hence for x=11 y=2, 11*3 = odd
for x=11 y=3, 11*4 =even
Hence the answer should be E
"x and y are prime"
x(y+1)
for x=2 and y=3 , 2*4=Even
for x=3 and y=2, 3*3=Odd
Hence, insufficient
Second Statement "x>7" is insufficient coz x can be even making the product even or x and y can both be odd making the product odd.
Together Also
x=11,13....
y=2,3,5 etc
Hence for x=11 y=2, 11*3 = odd
for x=11 y=3, 11*4 =even
Hence the answer should be E