Is x + y > 0?
(1) x^2 - y^2 > 1
(2) x/y + 1 > 0
The OA is the option E.
Using both statements together is not sufficient to solve this DS question?
Experts, may you give me some help? Thanks.
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Is x + y > 0 ?
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(1) x and/or y could be negative, so we don't have info to compare them INSUFFICIENTVincen wrote:Is x + y > 0?
(1) x^2 - y^2 > 1
(2) x/y + 1 > 0
The OA is the option E.
Using both statements together is not sufficient to solve this DS question?
Experts, may you give me some help? Thanks.
(2) We don't know if y is negative, so again it is INSUFFICIENT
STATEMENT (1) is the difference of 2 squares:
x^2 - y^2 = (x + y)(x - y) > 1
If x + y > 0, then (x - y) is positive, therefore x > y
STATEMENT (2) - if x and y are both positive, x>y (from (2)) then yes...
However, if say, x = 2 and y = 1, -1, ,-2 then x/y = 2, -2, -1... INSUFFICIENT
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Hi Vincen,
We're asked if X + Y is greater than 0. This is a YES/NO question and we can solve it by TESTing VALUES.
1) X^2 - Y^2 > 1
IF.... X = 2, Y = 1, then 2+1 IS greater than 0 and the answer to the question is YES.
IF.... X = -2, Y = -1, then -2 + (-1) is NOT greater than 0 and the answer to the question is NO.
Fact 1 is INSUFFICIENT.
2) (X/Y) + 1 > 0
The same TESTs we used in Fact 1 also 'fit' Fact 2:
IF.... X = 2, Y = 1, then 2+1 IS greater than 0 and the answer to the question is YES.
IF.... X = -2, Y = -1, then -2 + (-1) is NOT greater than 0 and the answer to the question is NO.
Fact 2 is INSUFFICIENT.
Combined, we don't have to do any additional work; the TESTs that we have already fit BOTH Facts and lead to 2 different answers (one "YES" and one "NO").
Combined, INSUFFICIENT
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
We're asked if X + Y is greater than 0. This is a YES/NO question and we can solve it by TESTing VALUES.
1) X^2 - Y^2 > 1
IF.... X = 2, Y = 1, then 2+1 IS greater than 0 and the answer to the question is YES.
IF.... X = -2, Y = -1, then -2 + (-1) is NOT greater than 0 and the answer to the question is NO.
Fact 1 is INSUFFICIENT.
2) (X/Y) + 1 > 0
The same TESTs we used in Fact 1 also 'fit' Fact 2:
IF.... X = 2, Y = 1, then 2+1 IS greater than 0 and the answer to the question is YES.
IF.... X = -2, Y = -1, then -2 + (-1) is NOT greater than 0 and the answer to the question is NO.
Fact 2 is INSUFFICIENT.
Combined, we don't have to do any additional work; the TESTs that we have already fit BOTH Facts and lead to 2 different answers (one "YES" and one "NO").
Combined, INSUFFICIENT
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
