A book has 999 pages. If a page is opened at random the probability that the sum of the digits in its number is 9, is

Total number of cases = 999 Favorable cases.The page number can be with all identical digits, i.e. 333→1 The identical and one different like 009, 117, 225 and 441 →4×3!2!=12 All different digits like 018,027,036,045,126,135,234 →7×3!=42 So favorable cases= 55Desired probability =55999