Data Sufficiency

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

Is the answer A?

guynoor wrote:

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

Working on it...

guynoor wrote:

guynoor wrote:

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

Both (1) and (2) are alone sufficient...am i right?

bicilotti wrote:

Is the answer A?

I tought so, gmatprep says C...

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

gabriel wrote:

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

given that (-a ,b) and (-b,a) are in the same quadrant .. that means both a and b have tha same sign .. that is they are eoither both positive ( in which case the 2 points are both are in the second quadrant ) or they are both negative ( in which case the 2 points are in the 4th quadrant )..

now the first statement says that xy>0.. so x and y have the same sign (they are either positve or negative ) .. that means (-x,y) is either in the 2nd or the 4th quadrant .. but since we dont know what is the positoin of (-a,b) and(-b,a) .. we dont have a defnite answer .. so not sufficient..

the second statement says that ax>0 .. again we have a,x and b (bcoz a and b have the same sign ) have the same sign ..but since we dont know the sign of y the statemant is insufficient..

now combine the 2 statements .. we have from the first statemnt x, y have the same sign ... from the 2nd statement we have a,x have the same sign .. so we get a,b,x,y have the same sign .. so now we can conclusively say that all the three points lie in the same quadrant ... if they are positive they will lie in the 3rd quadrant .. if they are negative the points will lie in the 4 th quadrant .. so the answer is C

guynoor wrote:

gabriel wrote:

bicilotti wrote:Two points (-a,b) (-b,a) are in the same quadrant of the xy plane. Is the point (-x,y) in the same plane?

(i) xy>0
(ii) ax>0

Getting mad, help please!

given that (-a ,b) and (-b,a) are in the same quadrant .. that means both a and b have tha same sign .. that is they are eoither both positive ( in which case the 2 points are both are in the second quadrant ) or they are both negative ( in which case the 2 points are in the 4th quadrant )..

now the first statement says that xy>0.. so x and y have the same sign (they are either positve or negative ) .. that means (-x,y) is either in the 2nd or the 4th quadrant .. but since we dont know what is the positoin of (-a,b) and(-b,a) .. we dont have a defnite answer .. so not sufficient..

the second statement says that ax>0 .. again we have a,x and b (bcoz a and b have the same sign ) have the same sign ..but since we dont know the sign of y the statemant is insufficient..

now combine the 2 statements .. we have from the first statemnt x, y have the same sign ... from the 2nd statement we have a,x have the same sign .. so we get a,b,x,y have the same sign .. so now we can conclusively say that all the three points lie in the same quadrant ... if they are positive they will lie in the 3rd quadrant .. if they are negative the points will lie in the 4 th quadrant .. so the answer is C

Doesn't it matter that they already provide you with -ve signs for both a and b as x and y coordinates for the 2 points. If thats the case then we know for sure that the 2 point would be in the 2nd Quad...If there can be the possibility if being in 2 Quadrants why even give the 2 -ve signs, why didn't they just give (a,b) and (b,a)???