Answer: n!/(n₁! n₂! ... nk!).
- A n!
- B n!/(n₁! n₂! ... nk!)
- C n!/(n₁+n₂+...)
- D n × n!
Correct answer: B. n!/(n₁! n₂! ... nk!)
Explanation: Multinomial coefficient: start with n! total arrangements, divide by n₁! for identical group 1, n₂! for group 2, etc. Result: n!/(n₁!n₂!…nk!).
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections