A three digit number n is such that the last two digits of it are...

If the last two digits is 0,0 , then in Ist digit any of the numbers except 0 i.e., 9 numbers If the last two digits is 1,1 , then in Ist digit any of the numbers except 0 and 1 , i.e. 8 numbers $\therefore$ The total number of numbers $=9+8 \times 9=81$