Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn bears a number which is a multiple of 3 ?

Answer: Option A

Here, S = {1, 2, 3, 4,........, 19, 20}
Let E = even of getting a multiple of 3 = {3, 6, 9, 12, 15, 18}
$$\therefore P(E)=\frac{n(E)}{n(S)}=\frac{6}{20}=\frac{3}{10}$$