If x and y are integers, is the value x(y+1) even ?
1. x and y are prime numbers
2. y > 7
I went with A. Because I thought x and y could be any prime numbers from 2 to n. Apart from number 2 all prime numbers are odd. So x(y+1) will have atleast one even number making it even. Am I wrong ? The solution from GMATPrep is C.
Please let me know, I'm going to give exam on Saturday . Don't feel quite prepared.
Thanks.
x(y+1) even ? provided x and y are prime numbers
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- Stuart@KaplanGMAT
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If you pick x = 3 and y = 2, then x(y+1) = 3(3) = 9 which is odd. Only by adding in y>7 do we know that y must be an odd integer, which means that x(y+1) = x(even) = even.crackitpal wrote:If x and y are integers, is the value x(y+1) even ?
1. x and y are prime numbers
2. y > 7
I went with A. Because I thought x and y could be any prime numbers from 2 to n. Apart from number 2 all prime numbers are odd. So x(y+1) will have atleast one even number making it even. Am I wrong ? The solution from GMATPrep is C.
Please let me know, I'm going to give exam on Saturday . Don't feel quite prepared.
Thanks.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
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Thank you very much Stuart!! I think just when your mind is supposed tobe responding, it fails to do so
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maybe its too late,,maybe i just don't get it
i don't get this one..can anyone explain it in more detail pls?
i don't get this one..can anyone explain it in more detail pls?
Hi Stuart.
In regard to solution provided to this problem long time ago, I may be asking a silly question, but would like
to clarify your solution.
Below you say y>7 = even, but y could be 8,9,10.... and by adding 1 , it would make it even or odd,
therefore it is not only even but also odd... I think I may be missing something here,
could you please clarify at earliest.
Thanks in advance.
Parag
In regard to solution provided to this problem long time ago, I may be asking a silly question, but would like
to clarify your solution.
Below you say y>7 = even, but y could be 8,9,10.... and by adding 1 , it would make it even or odd,
therefore it is not only even but also odd... I think I may be missing something here,
could you please clarify at earliest.
Thanks in advance.
Parag
Stuart Kovinsky wrote:If you pick x = 3 and y = 2, then x(y+1) = 3(3) = 9 which is odd. Only by adding in y>7 do we know that y must be an odd integer, which means that x(y+1) = x(even) = even.crackitpal wrote:If x and y are integers, is the value x(y+1) even ?
1. x and y are prime numbers
2. y > 7
I went with A. Because I thought x and y could be any prime numbers from 2 to n. Apart from number 2 all prime numbers are odd. So x(y+1) will have atleast one even number making it even. Am I wrong ? The solution from GMATPrep is C.
Please let me know, I'm going to give exam on Saturday . Don't feel quite prepared.
Thanks.
- Stuart@KaplanGMAT
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Hi,750Goal wrote:Hi Stuart.
In regard to solution provided to this problem long time ago, I may be asking a silly question, but would like
to clarify your solution.
Below you say y>7 = even, but y could be 8,9,10.... and by adding 1 , it would make it even or odd,
therefore it is not only even but also odd... I think I may be missing something here,
could you please clarify at earliest.
Thanks in advance.
Parag
that's in reference to why C (together) is the correct answer; only by adding y>7 to the first statement (y is prime) do we know that y must be odd.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
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- jeffedwards
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Another way you can think of it is, the statement is asking is at least one of the following statements true: x is even, or y is odd
We know that an even number times any number is even. Since an odd plus one would be even, if either of these statements is true we know that the answer is even.
I like to break up the question before even attacking the problem. This helps me a lot.
We know that an even number times any number is even. Since an odd plus one would be even, if either of these statements is true we know that the answer is even.
I like to break up the question before even attacking the problem. This helps me a lot.
- nikhilkatira
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Combining both statements say y is a prime no greater than 7capthan wrote:Hi Stuart,
x can be 2 or 3 and in both case x is prime, and if y>7 it will give you two different answers. IMO the answer is e.
Therefore y is odd
y+1 = even
X * ( y+1) = even irrespective of x
Best,
Nikhil H. Katira
Nikhil H. Katira
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Stuart, I still have a doubt. If x can be odd or even, and y is odd, then there are two probable answers and thus the answer must be (E).
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