Data Sufficiency

Hi melguy,

I'm going to give you a hint, then have you try this question again.

First, this is a YES/NO question; it's asking if x^2 + y^2 > 3z? It doesn't tell you ANYTHING about the variables. Second, is it possible that some (or all) of these variables = 0?

GMAT assassins aren't born, they're made,
Rich

Hi melguy,

There are ultimately 2 measures of "success" when choosing to answer a GMAT question:

1) Did you get the question correct?
2) How long did it take to do so?

If counting on your fingers is the fastest way that you can come up with to answer a question, then count on your fingers! Most GMAT questions have several potential approaches to solving, so flexibility on your part is a must (especially if you want to develop strong pacing skills). With what you've just learned, was the question made faster and easier to solve? Then remember these ideas the next time you face a similar question.

GMAT assassins aren't born, they're made,
Rich

melguy wrote:
There are 3 variables and 2 equations. Hence we should be able to find the value of x and y.

I should point out that the question isn't asking us to find the individual values of x, y and z. So, the rule about needing K different equations to solve a system with K variables doesn't apply here. Also, the question features inequalities, which also negates the rule.

For example, let's leave the target question as is (Is x^2 + y^2 > 3z?)
If statement 2 were "z < 0," then we'd have sufficient information to answer the target question. Here's why:
If z < 0, then 3z is negative
x^2 + y^2 will always be greater than or equal to zero.
So, it must be true that x^2 + y^2 > 3z

Cheers,
Brent