Question 18
The sum of the digits of all counting numbers less than $13$ is
$$
1+2+3+4+5+6+7+8+9+1+0+1+1+1+2=51
$$
Find the sum of the digits of all counting numbers less than $1000$.
$$
1+2+3+4+5+6+7+8+9+1+0+1+1+1+2=51
$$
Find the sum of the digits of all counting numbers less than $1000$.