Answer: 54.
- A 48
- B 54
- C 60
- D 66
Correct answer: B. 54
Explanation: Diagonals = n(n−3)/2 = 12·9/2 = 54.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections