sachin_yadav wrote:If zt < -3, is z < 4 ?
(1) z < 9
(2) t < -4
Target question: Is z < 4 ?
Given: zt < -3
Statement 1: z < 9
Since statement 1 does not
FEEL sufficient to me (because we're given information about only 1 value), I'm going to TEST values of z and t (values that satisfy the given conditions).
Case a: t = -5 and z = 1, in which case
z IS less than 4
Case b: t = -5 and z = 5, in which case
z is NOT less than 4
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: https://www.gmatprepnow.com/articles/dat ... lug-values
Statement 2: t < -4
This statement does not FEEL sufficient either, so let's test some values.
Case a: t = -5 and z = 1, in which case
z IS less than 4
Case b: t = -5 and z = 5, in which case
z is NOT less than 4
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Notice that, when testing values, I used values that satisfied BOTH statements.
So, COMBINED, the two statements yield conflicting answers to the target question:
Case a: t = -5 and z = 1, in which case
z IS less than 4
Case b: t = -5 and z = 5, in which case
z is NOT less than 4
Since we still cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer =
E
Cheers,
Brent
Just remember that the killer on the GMAT isn't the high-level stuff. It's the careless mistakes and the questions engineered to look much harder than they are.
