Question 5
Permutations and CombinationsIf nC2 = 15, find the value of n.
- A.8
- B.7
- C.6
- D.5
Show the answer and explanation
Answer: C (6)
Explanation
n(n − 1)/2 = 15 gives n² − n − 30 = 0, (n − 6)(n + 5) = 0, so n = 6.
If nC2 = 15, find the value of n.
Answer: C (6)
n(n − 1)/2 = 15 gives n² − n − 30 = 0, (n − 6)(n + 5) = 0, so n = 6.