Answer: 12 (O repeated twice).
- A 12, from treating BOOK as having all distinct letters
- B 24, computed as 4! without adjusting for the repeated letter
- C 12 (O repeated twice)
- D 4, counting only the distinct letters B, O, K
Correct answer: C. 12 (O repeated twice)
Explanation: BOOK: 4 letters with O repeated twice. 4!/2! = 12.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections