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* From S1, we know that \(xy=6\) , but we do not know what is \(x+y\) . Insufficient * From S2, we know that \(x\) is a prime number, but there is no information about \(y\) . Insufficient

Combining the statements, we know that \(xy=6\) . So \(x\) is a prime number and \(x>y\) , therefore \(y=2\) . The problem can then be solved. The correct answer is C.

---------------------------------------------------------- But what happens if X & Y are negative as thats a possbility? So the answer must be E

Re: M02 Q14, what if the X and y are negative? [#permalink]
27 Mar 2013, 05:50

2

This post received KUDOS

Expert's post

TheNona wrote:

chose A ... x+y is not known but has a fixed value .... therefore sufficient . Can anybody please explain why this cannot be correct?

When a DS question asks about the value of some variable (or an expression with variable(a)), then the statement(s) is sufficient ONLY if you can get the single numerical value of this variable (expression).

x and y are positive integers and x > y . What is the value of xy^2 + yx^2 ?

What is the value of \(xy^2 + yx^2=xy(y+x)\)?

(1) xy = 6 --> \(xy(y+x)=6(y+x)\). Now, since x and y are positive integers and x > y, then from xy = 6 it follows that x=6 and y=1 OR x=3 and y=2, thus 6(y+x)=42 or 6(y+x)=30. Two different values, thus this statement is NOT sufficient.

(2) x is a prime number. Clearly insufficient.

(1)+(2) Since from (2) we know that x is a prime number, then x=3=prime and y=2, thus 6(y+x)=42. Sufficient.

Re: m02. Q14, what if the X and y are negative? [#permalink]
05 Mar 2009, 05:20

Forrester300 wrote:

\(x\) and \(y\) are positive integers and \(x > y\) . What is the value of \(xy^2 + yx^2\) ?

1. xy = 6 2. x is a prime number

(C) 2008 GMAT Club - m02#14

* Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient * Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient * BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient * EACH statement ALONE is sufficient * Statements (1) and (2) TOGETHER are NOT sufficient

\(xy^2+ yx^2 = xy(x+y)\)

* From S1, we know that \(xy=6\) , but we do not know what is \(x+y\) . Insufficient * From S2, we know that \(x\) is a prime number, but there is no information about \(y\) . Insufficient

Combining the statements, we know that \(xy=6\) . So \(x\) is a prime number and \(x>y\) , therefore \(y=2\) . The problem can then be solved. The correct answer is C.

---------------------------------------------------------- But what happens if X & Y are negative as thats a possbility? So the answer must be E

2 things to note:

1. x and y are +ves 2. x is a prime, which can never be -ve.

Re: M02 Q14, what if the X and y are negative? [#permalink]
10 Nov 2009, 21:50

The solution can be reached even if X>Y not given (because value of X is not asked, so it doesn't matter as long as we find out that X can be either 2 or 3 and depending on the value of X, Y can be one of 2 or 3). So unless "X>Y" is meant to be a red herring, it can be removed from the Q.

* From S1, we know that \(xy=6\) , but we do not know what is \(x+y\) . Insufficient * From S2, we know that \(x\) is a prime number, but there is no information about \(y\) . Insufficient

Combining the statements, we know that \(xy=6\) . So \(x\) is a prime number and \(x>y\) , therefore \(y=2\) . The problem can then be solved. The correct answer is C.

---------------------------------------------------------- But what happens if X & Y are negative as thats a possbility? So the answer must be E

Its C. explanation given above. It is given that x & y are (+)ve.

Re: M02 Q14, what if the X and y are negative? [#permalink]
19 Mar 2010, 06:29

Question is saying that both the numbers are positive integers, so there is no question of considering the case when they are negative. _________________

Re: M02 Q14, what if the X and y are negative? [#permalink]
22 Mar 2011, 04:57

Question stem reworded: What's the value of XY (Y + X) when x & Y are positive integers and x > y?

1) xy = 6. We still need to determine (Y+X) (insufficient)

2) X is prime. X can be 2, 3, 5, 7, etc and we know nothing of Y (insufficient)

1 and 2) Together, xy=6. Therefore x or y has to be an even integer. Since x is prime and larger than Y, X has to be 3 and Y 2. Both statements together provide that Xy(Y+X) = 30

Re: M02 Q14, what if the X and y are negative? [#permalink]
27 Mar 2013, 05:36

chose A ... x+y is not known but has a fixed value .... therefore sufficient . Can anybody please explain why this cannot be correct? _________________

Re: M02 Q14, what if the X and y are negative? [#permalink]
27 Mar 2013, 06:15

Bunuel wrote:

TheNona wrote:

chose A ... x+y is not known but has a fixed value .... therefore sufficient . Can anybody please explain why this cannot be correct?

When a DS question asks about the value of some variable (or an expression with variable(a)), then the statement(s) is sufficient ONLY if you can get the single numerical value of this variable (expression).

x and y are positive integers and x > y . What is the value of xy^2 + yx^2 ?

What is the value of \(xy^2 + yx^2=xy(y+x)\)?

(1) xy = 6 --> \(xy(y+x)=6(y+x)\). Now, since x and y are positive integers and x > y, then from xy = 6 it follows that x=6 and y=1 OR x=3 and y=2, thus 6(y+x)=42 or 6(y+x)=30. Two different values, thus this statement is NOT sufficient.

(2) x is a prime number. Clearly insufficient.

(1)+(2) Since from (2) we know that x is a prime number, then x=3=prime and y=2, thus 6(y+x)=42. Sufficient.

Answer: C.

Hope it's clear.

yessssssssssssssssss ... I did not consider the option of 6& 1... only 2&3 . Thanks Bunuel _________________