NDA2013MathematicsPermutation and CombinationActual
If C (28,2 r)= C (28,2 r-4) , then what is r equal to?
Options
- A7
- B8
- C12
- D16
Correct answer
B. 8
Step-by-step solution
aligned & ²⁸ C _ 2 r = ²⁸ C _ 2 r-4 & 2 r+2 r-4=28 & 4 r=32 & r=8 aligned