Let . For , let be the number of subsets of , each containing five elements out of which exactly are odd. Then
- (A)210
- (B)252
- (C)125
- (D)126✓ Correct
Answer: (D)
Solution
The set contains 5 odd numbers and 4 even numbers .
Any subset of with 5 elements must contain at least 1 odd number (since there are only 4 even numbers).
Therefore, equals the total number of 5-element subsets of :
Any subset of with 5 elements must contain at least 1 odd number (since there are only 4 even numbers).
Therefore, equals the total number of 5-element subsets of :
JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Single correct option