Question

Tickets numbered from 1 to 20 are mixed up together and then a drown at random. What is the probability that the ticket has a number which is a multiple of 30 or 7?

Answer 1

Out of 20 tickets numbered from 1 to 20, one can be chosen in 20m ways. So, total number of elementary events associated with the given random experiment is 20. Out of 20 tickets numbered 1 to 20, tickets bearing numbers which are multiple of 3 or 7 bear numbers 3,6,7,9,12,14,15 and 18.
Favourable number of elementary events = 8
Hence, required probability = $\frac{8}{20}$ = $\frac{2}{5}$