The total number of three digit number which have two or more consecutive digits identical is

Answer:- 1

Explanation:-

Solution:

In each set of 100 numbers, there are 10 numbers whose tens digit and unit digit are same. Again in the same set there are 10 numbers whose hundreds and tens digits are same. But one number in each set of 100 numbers whose Hundreds, Tens and Unit digit are same as 111, 222, 333, 444 etc Hence, there are exactly (10 + 10 - 1) = 19 numbers in each set of 100 numbers. Further there are 9 such sets of numbers Therefore such total numbers = 19 × 9 = 171 Alternatively,

9 × 10 × 10 - 9 × 9 × 9 = 900 - 729 = 171