Is x y? (1) 9x = 4y (2) x = -y

Question

Is x > y?

(1) 9x = 4y
(2) x = -y

Vyacheslav · Answer

(1) 9x=4y
Restating statement, we receive x=4/9y,
4/9y<y, while y>0, and
4/9y>y, while y<0. While we cannot determine sign of x or y, (1) alone is NOT SUFFICIENT.

(2) x=-y
x>y for all x>0, and
x<y for all x<0. But again sign of x or y is not known. So, (2) alone is NOT SUFFICIENT.

Both statements together could be true only if x=y=0.

Answer should be C.

KUDOS if you find it helpful

AKProdigy87 · Answer

Statement 1: 9x = 4y

x = (4/9)y

Therefore,

If y < 0: x > y
If y > 0: x < y
If y = 0: x = y

Insufficient.

Statement 2: x = -y

If y < 0: x > y
If y > 0: x < y
If y = 0: x = y

Insufficient.

Both Statements Together

(1) 9x = 4y
(2) x = -y

It should be apparent that this is only true iff x = y = 0. Therefore, sufficient!

The answer is C.

mbaiseasy · Answer

Thank you for this question. here is my solution.

1.  9x=4y  also means:
(a)  \frac{x}{y}=\frac{4}{9}  which means y > x NO!
(b)  \frac{x}{y}=\frac{{-4}}{{-9}}  which means x > y YES!
INSUFFICIENT!

2.  \frac{x}{y}=-1  this means:
(a) they have the same number but of different sign, one is negative the other is positive BUT we don't know which one is positive or negative
(b) x = y = 0 
INSUFFICIENT!

Combine both:
 9(-y) = 4y 
 13y = 0 
 y=0  and  x=0

Answer: C

egmat · Answer

Another simpler approach could be... Statement 1- Say x= 4, & y=9 => x NO. But if x= -4, & y=-9 => x>y => Yes. Insufficient Statement 2- Say x= 1, & y=-1 => x>y => Yes. But if x= -1, & y=1 => x No. Insufficient Statement 1, & 2 together- Only one case is possible => x=y=0. Answer C. -Shalabh Jain

DensetsuNo · Answer

1) NS  
if x=4 & y=9 the statement is  sufficient ; 
but if x=9 & y=4 the statement is  insufficient ;

2) NS 
if  x=-y  is  -y>y ? 
It depends on whether y is negative.

T) S 
Is y negative?  -y > y , 
substitute in the second prompt and we get  \frac{x}{y}=\frac{4}{9}  ->  \frac{-y}{y}=\frac{4}{9}  ->  -1=\frac{4}{9} 
-> Impossible: y is never negative and x>y is never true.

Answer C.

GMATBusters · Answer

Is x > y?

(1) 9x = 4y
(2) x = -y

If we observe both equations, 
from 1st equation, both x and y have same sign
from 2nd equation, both x and y have opposite sign.
hence this is possible only when both x and y = 0

hence Combination of both statements is the sufficient, and Answer to question stem (Is x > y?) is No,

Answer C

rahul16singh28 · Answer

1 & 2 Alone are not sufficient.. Combining the two, we get -

9(x+y) = 13y

From Statement II,  x + y = 0

So,  9 * 0 = 13y

y =0, x = 0.

Hence, C.

GMATBusters · Answer

hi

9(x+y) = 13y 
what makes u conclude  y =0, x = 0. 
Reasoning is more important than the answer.

rahul16singh28 · Answer

Hi  gmatbusters

From Statement 1, we can write - 
 9(x+y) = 13y

From Statement B - 
 x + y = 0

So, we have by combining two statements -

9(x+y) = 13y  or
 9*0 = 13y

y = 0, x = 0

GMATBusters · Answer

yes, this is a complete explanation.

Hi gmatbusters From Statement 1, we can write - 9(x+y) = 13y From Statement B - x + y = 0 So, we have by combining two statements - 9(x+y) = 13y or 9*0 = 13y y = 0, x = 0

bumpbot · Answer

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Is x > y? (1) 9x = 4y (2) x = -y

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