The
number of ways in which a mixed double tennis game can be arranged amongst 9
married couples if no husband and wife play in the same game is:
(A) 1514
(B) 1512
(C) 3024
(D)
None of the above
Solution:
It
involves selection of 2 men and 2 women first and then arrangements in between
the pairs.
To
select 2 men from the given 9 men ------ 9C2 ways
To select 2 women from the given 9 women excluding the two, who are
wives of already selected 2
men ------ 7C2 ways
After selecting M1, M2, W1 and W2, the set of pairs may be
{(M1,W1)
and (M2,W2)} Or
{(M1,W2)
and (M2,W1)} ----2
possibilities
Hence the total number of arrangements = 9C2 * 7C2 * 2
=
(9*8/2) * (7*6/2) * 2 = 1512
Answer (B)