Question : A three-digit number is selected at random from the set of all three-digit numbers. The probability that the number selected has all the three digits same is
Answer : option (D)
Three-digit numbers are 100,101, …999. Total number of such numbers is 900. The three-digit numbers (which have all same digits) are 111,222, 333, …, 999. Favourable number of cases is 9. Therefore, the required probability is 9/900 = 1/100.