Hi All,
Roman Numeral questions are relatively rare on Test Day (you'll probably see just one in the Quant section), but they almost always come with some type of built-in 'shortcut' so that you can avoid some of the implied work.
Here, we're given a number line and told that the "ticks" for X, Y and Z are EVENLY SPACED. This means that the distance between any two ticks is the SAME. We're asked which of the three statements MUST be true, which really means "which of these is ALWAYS TRUE no matter how many different examples we can come up with?"
From the picture, there is an immediate set of deductions that can be made about the 3 variables:
X is NEGATIVE (it's to the "left" of 0)
Y and Z are POSITIVE (they're to the "right" of 0)
RN 1: XYZ < 0
With the information we noted above....
(X)(Y)(Z) = (-)(+)(+) = ALWAYS Negative
Roman Numeral 1 is ALWAYS TRUE
Eliminate Answers B and C.
RN 2: X+Z = Y
Noting the picture, we know that....
X = "-1 tick"
Y = "+1 tick"
Z = "+2 ticks"
X+Z = "-1 tick" + "2 ticks" = "+1 tick"
This equals the value of Y (which is "+1 tick")
Roman Numeral 2 is ALWAYS TRUE.
Eliminate Answers A and D.
We don't even need to check Roman Numeral 3.
Final Answer:
GMAT assassins aren't born, they're made,
Rich