Find the probability that a number selected at random from 21 to 34 is a multiple of 3

Find the probability that a number selected at random from 21 to 34 is a multiple of 3

Answer Details

S = {21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34}
n(S) = 14
multiples of 3 = {21, 24, 27, 30, 33}
n(multiples of 3) = 5
Prob( picking a multiple of 3) = 5/14