9. (5 points) A division operation, the dividend is 10, the divisor is less than 10, then the sum of all possible different remainders is . $\qquad$
【Analysis】The divisor is less than 10, so we can divide 10 by $1 \sim 9$, and among the remainders obtained, there are 2 that are 0, i.e., the remainder is 0 when dividing by $1$ and $5$. The different remainders are $1, 2, 3, 4$. We can then find the sum.

【Solution】According to the analysis, $10 \div 6=1 \cdots 4$;
$$
\begin{array}{l}
10 \div 7=1 \cdots 3 ; \quad 10 \div 8=1 \cdots 2 ; \\
10 \div 9=1 \cdots 1 ;
\end{array}
$$

And $10 \div 3$ and $10 \div 9$ both have a remainder of $1$, $10 \div 4$ and $10 \div 8$ both have a remainder of 2,
so the different remainders are only: $1, 2, 3, 4$,
the sum of all possible different remainders $=1+2+3+4=10$.
Therefore, the answer is: 10