Total no. of possible outcomes = 30 {1, 2, 3, … 30}

E ⟶ event of getting no. divisible by 3.

No. of favourable outcomes = 10 {3, 6, 9, 12, 15, 18, 21, 24, 27, 30}

Probability, P(E) = (No.of favorable outcomes)/(Total no.of possible outcomes)

P(E) = 10/30 = 1/3

Bar E ⟶ event of getting no. not divisible by 3.

P(Bar E) = 1 – P(E)

= 1 - 1/3 = 2/3