Question

the probability that a number select from 1,2,3,4...19 and 20 will be a multiple of 5 _______​

Answer 1

there is four multiples of 5 in the set {1,2,3,4,...,20}.

therefore, the probability of getting a multiple of 5 is: number of required events / total observations

which is,

4/20 = 1/5

hope it helps ;)