Todd recently competed in a dance contest. The contest had exactly 4 judges, each of whom gave Todd an integer...
GMAT Data Sufficiency : (DS) Questions
Todd recently competed in a dance contest. The contest had exactly \(\mathrm{4}\) judges, each of whom gave Todd an integer rating from \(\mathrm{1}\) to \(\mathrm{10}\). Todd received a mean rating of \(\mathrm{7.5}\). Did any judge give Todd a rating of \(\mathrm{10}\)?
- One judge gave Todd a rating of \(\mathrm{2}\)
- Each of \(\mathrm{3}\) judges gave Todd ratings of \(\mathrm{8}\) or higher.
Understanding the Question
We need to determine if any judge gave Todd a rating of 10.
Given Information
- 4 judges total
- Each judge gives an integer rating from 1 to 10
- Todd's mean rating = 7.5
- Therefore, total sum of ratings = \(4 \times 7.5 = 30\)
What We Need to Determine
This is a yes/no question. We need sufficient information to answer either:
- YES: At least one judge gave a 10, or
- NO: No judge gave a 10
The key insight: With exactly 30 points distributed among 4 integer ratings (each between 1-10), we're looking for whether a 10 must appear, can appear, or cannot appear in that distribution.
Analyzing Statement 1
Statement 1 tells us: One judge gave Todd a rating of 2
What This Means
If one rating is 2, then the remaining 3 ratings must sum to 28 (since \(30 - 2 = 28\)).
The Key Constraint
Here's the critical insight: We need to distribute 28 points among 3 ratings, where each rating is between 1 and 10.
Let's check if it's possible without using a 10:
- Maximum possible without a 10: three 9s = 27 points
- But we need: 28 points
- Since \(27 < 28\), we cannot reach the required sum without at least one 10
Verification Example
With one judge giving a 2, a valid rating set could be: {2, 9, 9, 10}
- Check: \(2 + 9 + 9 + 10 = 30\) ✓
Conclusion
Statement 1 is sufficient. We can definitively answer YES - at least one judge must have given Todd a 10.
[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 tells us: Each of 3 judges gave Todd ratings of 8 or higher
What This Means
- Three ratings are ≥ 8 each
- One rating could be anything from 1 to 10
- The three high ratings contribute at least 24 points (if all are 8s)
Testing Different Scenarios
Let's see if we can construct valid rating sets with and without a 10:
Scenario 1 - Without a 10:
- Three judges give: \(8 + 8 + 8 = 24\)
- Fourth judge must give: \(30 - 24 = 6\)
- Valid rating set: {8, 8, 8, 6} ✓
- Contains a 10? NO
Scenario 2 - With a 10:
- Three judges give: \(8 + 9 + 10 = 27\)
- Fourth judge must give: \(30 - 27 = 3\)
- Valid rating set: {8, 9, 10, 3} ✓
- Contains a 10? YES
Both scenarios satisfy all our constraints but give different answers to whether any judge gave a 10.
Conclusion
Statement 2 is NOT sufficient. We cannot determine whether any judge gave Todd a 10.
This eliminates choices B and D.
The Answer: A
Statement 1 alone forces at least one rating to be 10 (mathematical necessity), while Statement 2 allows scenarios both with and without a 10 (multiple possibilities).
Answer Choice A: "Statement 1 alone is sufficient, but Statement 2 alone is not sufficient."