JEE Advanced2017MathematicsSets and RelationsActual
Let S = 1,2 , 3 , … . 9 . For k = 1,2 , … 5 , let N k be the number of subsets of S , each containing five elements out of which exactly k are odd. Then N 1 + N 2 + N 3 + N 4 + N 5 =
Options
- A125
- B252
- C210
- D126
Correct answer
D. 126
Step-by-step solution
N 1 + N 2 + N 3 + N 4 + N 5 = Total ways – when no odd Total ways = 9 C 5 Number of ways when no odd, is zero ( ∵ only available even are 2 ,   4 ,   6 ,   8 ) ∴   9 C 5 - zero = 126