When a die is rolled three times.
Then, cardinality of sample space
=63 Now, according to question, the favourable outcomes
={ (1,2,3),(1,2,4),(1,2,5),(1,2,6)
(1,3,4),(1,3,5),(1,3,6),(1,4,5),
(1,4,6),(1,5,6),(2,3,4),(2,3,5),
(2,3,6),(2,4,5),(2,4,6),(3,4,5)
(3,4,6),(4,5,6),(2,5,6),(3,5,6) }
∴ Required probability
=‌=‌