If x=y-z, is x>y?

[Max@Math Revolution]

[GMAT math practice question]3.9

$$If\ x=y-z,\ is\ x>y?$$

$$1)\ y<0$$
$$2)\ z<0$$

[GMATinsight]

[GMAT math practice question]3.9

$$If\ x=y-z,\ is\ x>y?$$

$$1)\ y<0$$
$$2)\ z<0$$

Given, x = y - z
i.e. x - y = -z

Question : Is x > y?
Question : Is x - y > 0?
Question : Is -z > 0?

Question : Is z < 0?

Statement 1: y < 0
No Information about z hence
NOT SUFFICIENT

Statement 2: z < 0

SUFFICIENT

Answer: Option B

Key Take Away: Always rephrase the question in the simplest possible form so that we can objectively look at the information actually needed to solve the question

[Max@Math Revolution]

=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question.

We can modify the question as follows:
x>y
=> x-y > 0
=> -z > 0 by the original condition
=> z < 0
This is the same as condition 2).

Condition 1)
If x = -1, y = -2, and z = -1, x > y, and the answer is 'yes'.
If x = -2, y = -1, and z = 1, x < y, and the answer is 'no'.
Condition 1) is not sufficient since the question does not have a unique answer.

Therefore, B is the answer.

Answer: B