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?

Total numbers of elementary events are = 20

Let E be the event of drawing a multiple of 3

The favorable outcomes are: 3, 6, 9, 12, 15, 18

Total numbers of favorable outcomes are = 6

P (multiple of 3) = P (E) = 6/20 =3/10