Q.
Let A denote the event that a 6 -digit integer formed by 0,1,2,3,4,5,6 without repetitions, be divisible by 3 . Then probability of event A is equal to :
Total cases: 6⋅6⋅5⋅4⋅3⋅2 n(s)=6⋅6!
Favourable cases :
Number divisible by 3≡
Sum of digits must be divisible by 3 Case-I 1,2,3,4,5,6
Number of ways =6! Case-II 0,1,2,4,5,6
Number of ways =5⋅5! Case-III 0,1,2,3,4,5
Number of ways =5.5! n( favourable )=6!+2⋅5⋅5! P=6⋅6!6!+2⋅5⋅5!=94