DS questions

[anwarma]

IF xy = -18, is x less than y?

1) x <0

2) y < 10

ANS is A

Would greatly appreciate an explanation, Thanks!

[*arch*]

Given:- xy = -18

We can infer two possible situations from the above equation
x is negative, y is positive OR
x is negative, y is positive

Statement (1) says x<0; this implies that y is positive and we can conclude that x<y. Therefore, Statement (1) is sufficient.

Statement (2) says y<10; however, y can be positive or negative and this leads us nowhere! Therefore, Statement (2) is insufficient.

Answer is (A)... Hope this helps!

[amitdgr]

Given:- xy = -18

We can infer two possible situations from the above equation
x is negative, y is positive OR
x is negative, y is positive

I think *arch* made a typo here -
x is negative, y is positive OR
x is positive , y is negative

when the product of 2 numbers ( here x and y) is negative, then one of them is negative (i.e.) either x is negative OR y is negative.

only one of em can be -ve .. Stmt 1 says x<0 ( meaning x is -ve )
So y is positive. And a positive num is always greater than a negative number.

thus when x < 0 in the given expression , we can confidently say y > x

Statement 1 alone is sufficient. That means answer choice should be between A or D

Now looking at statement , y<10 does not give us concrete info about it being negative or positive. y can be 2 or 3 or -6 etc. Thus stmt 2 not suff

=> Answer choice A is correct .


HTH


Amit

[*arch*]

Thanks for pointing out the typo =]