NDA Math Probability

The given set = {1,2,3,4,5,6,7}
Odd set = {1,3,5,7}
Even set = {2,4,6}
Number of ways selecting odd number(Y) and even number(X) is 4C1×3C1
Where X + Y = 5
1 + 4 = 5
3 + 2 = 5
Therefore, two valid cases exist
Probability =

2

4C1×3C1

=

1

6