A certain economics report defines a middle-class family as a family whose income is at least half, but no more...
GMAT Data Sufficiency : (DS) Questions
A certain economics report defines a middle-class family as a family whose income is at least half, but no more than twice, the median family income. According to this report, is a family whose income is \(\$73,000\) considered a middle-class family?
- The median family income is \(\$37,152\)
- The minimum income of a middle-class family is \(\$18,576\)
Understanding the Question
We need to determine if a family earning $73,000 is considered middle-class.
Given Information
- Middle-class definition: Income must be between \(0.5 \times\) and \(2 \times\) the median family income
- Family in question earns: $73,000
- We need: A definitive YES or NO answer
What We Need to Determine
To answer this question, we need to know if $73,000 falls within the middle-class range. Since the range spans from \(0.5\mathrm{M}\) to \(2\mathrm{M}\) (where M is the median), this creates a \(4 \times\) span from minimum to maximum.
Key Insight
Rather than calculating exact boundaries, we can think proportionally. If we know either the median or one boundary, we can determine where $73,000 sits relative to the middle-class range.
Analyzing Statement 1
Statement 1: The median family income is $37,152
What Statement 1 Tells Us
With the median at $37,152, we can think about where $73,000 sits proportionally. Notice that $73,000 is approximately twice $37,152 (just under \(2 \times\)).
Logical Analysis
Since middle-class extends from \(0.5 \times\) to \(2 \times\) the median:
- The upper boundary is \(2 \times\) $37,152 (which would be about $74,000)
- The lower boundary is \(0.5 \times\) $37,152 (which would be about $18,500)
- $73,000 is clearly more than half the median and just under twice the median
Therefore, $73,000 falls within the middle-class range.
Conclusion
Statement 1 is SUFFICIENT to answer with a definitive YES.
[STOP - Sufficient!]
This eliminates choices B, C, and E.
Analyzing Statement 2
Now let's forget Statement 1 completely and analyze Statement 2 independently.
Statement 2: The minimum income of a middle-class family is $18,576
What Statement 2 Provides
We know the lower boundary of middle-class is $18,576. Since this represents \(0.5\mathrm{M}\), the upper boundary must be \(4 \times\) this amount (because \(2\mathrm{M} \div 0.5\mathrm{M} = 4\)).
Logical Analysis
The maximum middle-class income = \(4 \times\) $18,576 ≈ $74,000+
Now we can see that:
- $73,000 is well above the minimum of $18,576
- $73,000 is just below \(4 \times\) the minimum (approximately $74,000)
Therefore, $73,000 falls within the middle-class range.
Conclusion
Statement 2 is SUFFICIENT to answer with a definitive YES.
[STOP - Sufficient!]
The Answer: D
Both statements independently allow us to determine that $73,000 falls within the middle-class income range.
Answer Choice D: "Each statement alone is sufficient."