(Q). In how many ways can a mixed double game in Tennis be arranged from 20 married couples, if no husband and wife play in the same game.
Solution:-
2 men can be selected in ²⁰C₂ ways
and that can be done in ¹⁸C₂ ways
Now we have 2 men & 2 women & they can be pair up in 2 ways
Hence total number of ways = ²⁰C₂×¹⁸C₂×2 Answer