🎯 What are we trying to prove?
👉 Do at least 2 students share ALL 3:
- same gender
- same birth month
- same GMAT score
🧠 Build the “boxes”
Each student is classified by:
- Gender → 2
- Months → 12
- Scores → from 200 to 800 in steps of 10 → 61 possible scores
👉 Total distinct combinations:
2 × 12 × 61 = 1464 boxes
👀 Compare with students
- Students = 478
- Boxes = 1464
👉 478 < 1464 → NOT forced
So overall, duplicates are not guaranteed.
🔍 Statement (1)
Range = 600 to 780
Count scores:
(780 − 600)/10 + 1 = 19 scores
New boxes:
2 × 12 × 19 = 456
Now compare:
- Students = 478
- Boxes = 456
👉 478 > 456 → collision MUST happen
✅ Sufficient
🔍 Statement (2)
60% male → 40% female
But nothing about score range → still 61 scores.
Boxes per gender:
12 × 61 = 732
Compare:
- Males: 287 < 732 → no guarantee
- Females: 191 < 732 → no guarantee
❌ Not sufficient
✅ Final Answer:
👉 (1) alone is sufficient
👉 (2) alone is not
Answer: A