NDA2022MathematicsPermutation and CombinationActual
If C(3 n, 2 n)=C(3 n, 2 n-7) , then what is the value of C(n, n-5) ?
Options
- A42
- B35
- C28
- D21
Correct answer
D. 21
Step-by-step solution
Given that 3 n 2 n = 3 n 2 n-7 aligned & 2 A n+2 n-7=3 n & n=7 & ^n C_ n-5 = ^7 C₂= 7.6 2.1 =21 aligned