Answer: 10C5 / 2 = 126.
- A 10C5, the unsimplified combination count
- B 10C5 / 2 = 126
- C 10P5, treating order as significant
- D 252, double the actual correct count
Correct answer: B. 10C5 / 2 = 126
Explanation: 10C5 = 252. But groups are unordered (not labeled), so divide by 2: 252/2 = 126.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections