A three digit number $n$ is such that the last two digits of it are equal and differ from the first. The…
A three digit number $n$ is such that the last two digits of it are equal and differ from the first. The number of such $n$ 's is
64
72
81
900
Solution
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
$=9+8 \times 9=81$