Probability of numbers divisible by 9 from numbers 1-100?

11

(9, 18, 27, 36, 45, 54, 63, 72, 81, 90 and 99)

Those numbers divisible by 9 are the multiple of 9; thus need to know how many multiples of 9 there are between 1 and 100:

100 : 9 = 11 r 1 : last multiple of 9 is 11 * 9 ( = 99)

→ There are 11 - 1 + 1 = 11 numbers between 1 and 100 which are divisible by 9.

(They are 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99.)