Question

x is chosen at random from all integers between 1 and 20 inclusive. What is the probability that it is a multiple of 3?

Answer 1

Listing the multiples of 3 form 1 to 20:
3, 6, ...., 18

how many are there?
What is the prob ?

Answer 2

There are 20 numbers
There are 6 multiples of 3
So, P(x=3k) = 6/20