If y geq 0, what is the value of x? |x - 3| geq y |x - 3| leq -y...
GMAT Data Sufficiency : (DS) Questions
If \(\mathrm{y} \geq 0\), what is the value of \(\mathrm{x}\)?
- \(|\mathrm{x} - 3| \geq \mathrm{y}\)
- \(|\mathrm{x} - 3| \leq -\mathrm{y}\)
Understanding the Question
We need to find the exact value of x, given that \(\mathrm{y} \geq 0\).
This is a value question - we need to determine one specific value for x to have sufficiency.
Given Information
- \(\mathrm{y} \geq 0\) (y is non-negative)
- We need a unique value for x
What We Need to Determine
For sufficiency, we need information that either:
- Directly tells us what x equals, or
- Creates constraints that lead to exactly one possible value of x
Analyzing Statement 1
Statement 1: \(|\mathrm{x} - 3| \geq \mathrm{y}\)
What Statement 1 Tells Us
This tells us that the distance between x and 3 is at least y. Since we know \(\mathrm{y} \geq 0\), this means x is at least y units away from 3.
Testing Different Scenarios
Let's test with different values of y:
- If \(\mathrm{y} = 0\): Then \(|\mathrm{x} - 3| \geq 0\), which is true for ALL values of x (since absolute value is always non-negative)
- If \(\mathrm{y} = 2\): Then \(|\mathrm{x} - 3| \geq 2\), meaning \(\mathrm{x} \geq 5\) or \(\mathrm{x} \leq 1\)
In both cases, we get infinitely many possible values for x.
Conclusion
Statement 1 is NOT sufficient because x can take many different values.
This eliminates choices A and D.
Analyzing Statement 2
Now let's forget Statement 1 completely and analyze Statement 2 independently.
Statement 2: \(|\mathrm{x} - 3| \leq -\mathrm{y}\)
What Statement 2 Provides
This might seem tricky at first, but here's where it gets interesting. We know that:
- \(\mathrm{y} \geq 0\), so \(-\mathrm{y} \leq 0\) (non-positive)
- \(|\mathrm{x} - 3| \geq 0\) always (absolute values are never negative)
The Key Insight
We need \(|\mathrm{x} - 3| \leq -\mathrm{y}\), where:
- The left side (\(|\mathrm{x} - 3|\)) is always \(\geq 0\)
- The right side (\(-\mathrm{y}\)) is always \(\leq 0\)
Critical observation: The only way a non-negative value can be less than or equal to a non-positive value is if both equal zero!
This forces:
- \(|\mathrm{x} - 3| = 0\), which gives us \(\mathrm{x} = 3\)
- \(-\mathrm{y} = 0\), which gives us \(\mathrm{y} = 0\)
Let's verify: When \(\mathrm{x} = 3\) and \(\mathrm{y} = 0\):
- \(|3 - 3| = 0\)
- \(-0 = 0\)
- Indeed, \(0 \leq 0\) ✓
Conclusion
Statement 2 is sufficient because it forces \(\mathrm{x} = 3\). [STOP - Sufficient!]
This eliminates choices C and E.
The Answer: B
Statement 2 alone gives us the unique value \(\mathrm{x} = 3\), while Statement 1 alone allows infinitely many values.
Answer Choice B: "Statement 2 alone is sufficient, but Statement 1 alone is not sufficient."