If an integer is selected at random from 1 to 100. The probability that it relatively prime to 100 is?

From the set of odd number < 100, if we exclude multiples of 5, we get the set of numbers < 100 and relatively prime to 100.
The number of such numbers = 50 - 10 = 40
∴ Reqd. Probability = 40 / 100 = 2/5