The 50 participants of a management training seminar ate dinner at a certain restaurant. They had 3 choices for their...
GMAT Data Sufficiency : (DS) Questions
The \(50\) participants of a management training seminar ate dinner at a certain restaurant. They had \(3\) choices for their meal: vegetarian lasagna for \(\$12\), blackened catfish for \(\$15\), or stuffed pork chops for \(\$18\). Each participant ordered exactly \(1\) meal and the total cost of the meals ordered by the participants was \(\$810\). How many participants of the management training seminar ordered blackened catfish?
- Six more people ordered catfish than lasagna.
- Twice as many pork chop meals were ordered as catfish meals.
Understanding the Question
We need to find the exact number of participants who ordered blackened catfish.
Given Information
- Total participants: 50
- Three meal choices with fixed prices:
- Vegetarian lasagna: $12
- Blackened catfish: $15
- Stuffed pork chops: $18
- Each participant ordered exactly 1 meal
- Total cost of all meals: $810
What We Need to Determine
To answer "How many participants ordered blackened catfish?", we need a unique value for the number of catfish orders.
Let's define:
- \(\mathrm{L} = \mathrm{number\ who\ ordered\ lasagna}\)
- \(\mathrm{C} = \mathrm{number\ who\ ordered\ catfish}\)
- \(\mathrm{P} = \mathrm{number\ who\ ordered\ pork\ chops}\)
From our given information:
- \(\mathrm{L + C + P = 50}\) (total participants)
- \(\mathrm{12L + 15C + 18P = 810}\) (total cost)
Key Insight
With 2 equations and 3 unknowns, we need one more independent constraint to find a unique value for C. Think of it this way: we know the total headcount and total bill, but there are multiple ways to distribute 50 people among three meals to reach $810.
Analyzing Statement 1
Statement 1: Six more people ordered catfish than lasagna.
What Statement 1 Tells Us
This gives us the relationship: \(\mathrm{C = L + 6}\)
Now we have a third equation! This creates a system of 3 equations with 3 unknowns, which typically has a unique solution.
Solving the System
From \(\mathrm{C = L + 6}\), we get \(\mathrm{L = C - 6}\)
Substituting into our participant equation:
- \(\mathrm{(C - 6) + C + P = 50}\)
- \(\mathrm{2C + P = 56}\)
- \(\mathrm{P = 56 - 2C}\)
Now substituting both expressions into the cost equation:
- \(\mathrm{12(C - 6) + 15C + 18(56 - 2C) = 810}\)
- \(\mathrm{12C - 72 + 15C + 1008 - 36C = 810}\)
- \(\mathrm{-9C + 936 = 810}\)
- \(\mathrm{-9C = -126}\)
- \(\mathrm{C = 14}\)
Verification
Let's verify our answer:
- \(\mathrm{C = 14}\) (catfish orders)
- \(\mathrm{L = 14 - 6 = 8}\) (lasagna orders)
- \(\mathrm{P = 56 - 2(14) = 28}\) (pork chop orders)
Check: \(\mathrm{8 + 14 + 28 = 50}\) ✓
Cost: \(\mathrm{12(8) + 15(14) + 18(28) = 96 + 210 + 504 = 810}\) ✓
Conclusion
Statement 1 provides enough information to determine that exactly 14 participants ordered catfish.
[STOP - Statement 1 is Sufficient!]
This eliminates choices B, C, and E.
Analyzing Statement 2
Important: We now forget Statement 1 completely and analyze Statement 2 independently.
Statement 2: Twice as many pork chop meals were ordered as catfish meals.
What Statement 2 Provides
This gives us: \(\mathrm{P = 2C}\)
Again, we have a third equation, creating a solvable system.
Solving the System
From \(\mathrm{P = 2C}\) and our participant equation:
- \(\mathrm{L + C + 2C = 50}\)
- \(\mathrm{L + 3C = 50}\)
- \(\mathrm{L = 50 - 3C}\)
Substituting into the cost equation:
- \(\mathrm{12(50 - 3C) + 15C + 18(2C) = 810}\)
- \(\mathrm{600 - 36C + 15C + 36C = 810}\)
- \(\mathrm{600 + 15C = 810}\)
- \(\mathrm{15C = 210}\)
- \(\mathrm{C = 14}\)
Verification
Let's verify this solution:
- \(\mathrm{C = 14}\) (catfish orders)
- \(\mathrm{P = 2(14) = 28}\) (pork chop orders)
- \(\mathrm{L = 50 - 3(14) = 8}\) (lasagna orders)
Check: \(\mathrm{8 + 14 + 28 = 50}\) ✓
Cost: \(\mathrm{12(8) + 15(14) + 18(28) = 96 + 210 + 504 = 810}\) ✓
Conclusion
Statement 2 also provides enough information to determine that exactly 14 participants ordered catfish.
[STOP - Statement 2 is Sufficient!]
The Answer: D
Both statements independently provide enough information to determine that 14 participants ordered blackened catfish.
Answer Choice D: "Each statement alone is sufficient."