GMATprep

[tweety846]

Need help on the following GMATprep questions.. an early help might make a lot of difference.
Thanks a bunch all you guys out there!
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[tweety846]

Can someone confirm if the following answers are right?
I dont have the Official Answer

1) C
2) E
3) E

[lax696]

Question 1
I would say that the answer is D.

You know a few things from the question:

1. You know that either y is negative or that x and z are negative.
2. You know that if y is positive, then z is less than x (divide both sides of zy<xy by a positive y and you get z<x)
3. You know that if y is negative, then z is greater than x (divide both sides of zy<xy by a negative y and flip the sign and you get z>x)

Statement 1 - This tells you that z<x, so you know that y is positive. That means that both z and x need to be negative and z is smaller (more negative) than x.

Plug in a few examples and you'll see that it works when both numbers are negative and z is less than x. So A is sufficient.

Statement 2 - This statement tells you that y is positive. Again, you know that x and z are therefore negative and that z<x. B is sufficient.

The key to this question is realizing early that both statements tell you the same thing. They tell you that y is positive, that x and z are negative and that, therefore, z has to be less than x. If they tell you the same thing, either they both are sufficient or neither is. Which immediately gets you to D or E.

You could plug in numbers, as I did, or you could think about it this way. If z and x are both negative and z is less than x, then the equation changes into the following:
l-x+zl + x = z
Since z is smaller (or more negative), the absolute value signs become irrelevant on the first part of the equation (becuase the answer will always be positive). So the equation is as follows:
-x + z + x = z
Cancel out the x and the -x and you have z = z. Voila!

Of course, I could be totally wrong, which would mean that you shoudl ignore this completely. But that's how I would have done it.

[ash82]

I used the same logic... the ans for (1) should be D

[tweety846]

wow that was a nice take ! thanks for the wonderful explanation lax!