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 Z=X×Y
=1×2
=3×2
=5×2
=7×2
Therefore, four valid cases exist.
Probability=

4

4C1×3C1

=

1

3