Answer: nCr.
- A nPr
- B nCr
- C n!
- D r!
Correct answer: B. nCr
Explanation: Pascal triangle entries are binomial coefficients nCr. Row n (starting from 0) has entries nC0, nC1,...,nCn.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections