CA Foundation P3 · Chapter 5 · Question 9 of 9
If ⁿC₈ = ⁿC₁₂, then ⁿC₁₇ is equal to:
Test yourself: pick an answer
Reveal answer & explanation
Correct answer: B) 1140
Explanation
ⁿCᵣ = ⁿCₛ with r ≠ s implies n = r + s = 8 + 12 = 20. Then ²⁰C₁₇ = ²⁰C₃ = 20 x 19 x 18 / 6 = 1,140. ²⁰P₃ = 6,840 forgets to divide by 3!.
More Basic Concepts of Permutations and Combinations MCQs
- Q2In how many ways can a committee of 3 be chosen from 8 persons?
- Q3A committee of 5 is to be formed from 6 men and 4 women. In how many ways can this be done if the committee must contain exactly 2 women?
- Q4In how many ways can 7 persons be seated around a circular table?
- Q5How many 4-digit even numbers can be formed using the digits 1, 2, 3, 4, 5, 6, 7 if no digit is repeated?
- Q6If ⁿP₂ = 90, then n is: