Pick a Number

An integer is chosen at random from the set {21, 22, 23, ..., 81}. What's the probability that the chosen number is one more than a multiple or 4 or one more than a multiple of 5?

----------------------

A similar problem was given in Assignment 2 of Charlotte Math Meetup:

An integer is chosen at random from the set {41, 42, 43, ..., 67}. What's the probability that the chosen number is one more than a multiple or 4 or one more than a multiple of 5? (Please express the answer as a decimal number rounded to hundredth.)