Probability of composite and divisible numbers between 60 and 100

Numbers between 60 and 100 are $61, 62, ..., 99$. Total numbers $= 99 - 61 + 1 = 39$. Prime numbers between 60 and 100 are: 61, 67, 71, 73, 79, 83, 89, 97 (8 prime numbers). Number of composite numbers $= 39 - 8 = 31$. Probability $= \frac{31}{39}$.

Numbers between 60 and 100 divisible by 6 are: 66, 72, 78, 84, 90, 96 (6 numbers). Probability $= \frac{6}{39} = \frac{2}{13}$.