The positive integer is chosen randomly from the integers 1-100. There are a total 100 integers from which 1 is chosen. The number of integers in the set of numbers 1-100 that are divisible by 5 is 20.
The probability of an event taking place is given by the number of favorable events divided by the number of total possible events.
Here, this gives the probability of the randomly picked integer being divisible by 5 as 20/100 = 0.2
The probability that an integer chosen from the integers 1-100 is divisible by 5 is 0.2