Tickets numbered from 1 to 20 are mixed up together and then a ticket is drawn at random. What is the probability that the ticket has a number which is a multiple of 3 or 7?

Explanation

Here,`S = {1, 2, 3, 4, ...., 19, 20}`.
Let `E =` event of getting a multiple of `3` or `5 = {3, 6 , 9, 12, 15, 18, 5, 10, 20}`.
`P(E)=(n(E)) / (n(S))=9/20`