Let A denote the event that a 6-digit integer formed by 0,1,2,3,4,5,6 without repetition be divisible by 3. The probability of event A is equal to:
Option: 1
Option: 2
Option: 3
Option: 4
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! = 5! (6+10)
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