Six new employees, two of whom are married to each other, are to be assigned six desks that are lined up in a row. If the assignment of employees to desks is made randomly, what is the probability that the married couple will have nonadjacent desks?
Given: total number of employees = 6
They can be arranged in 6 ways:
Thus, n (S) = 6!
= 6 x 5 x 4 x 3 x 1
= 720
Now, there are 5 different ways to select two adjacent desks for married couples:
(1,2), (2,3), (3,4), (4,5), (5,6)
They can be arranged in two ways in the two desks, & the other persons can be arranged in four ways
Thus, the number of ways = 5 x 2! X 4!
= 5 x 2 x 1 x 4 x 3 x 2 x 1
= 240
Thus,
The number . of ways in which married couples occupy non-adjacent desks
= 6! – 240
= 720 – 240
= 480
= n (E)
Required probability = number of favourable outcomes/total number of outcomes
= n (E) / n (S)
= 480 / 720
= 2 / 3