11. (12 points) Junjun is looking at an incorrect one-digit multiplication equation $A \times B=\overline{C D}$ (where $A, B, C, D$ represent different digits). The clever Junjun discovers: if only one digit is changed, there are 3 ways to correct it. If only the order of $A, B, C, D$ is changed, it can also be corrected. Therefore, $A+B+C+D=$ $\qquad$ .
【Solution】Solution: By using the method of exhaustion, we know: The incorrect one-digit multiplication equation is: $2 \times 6=18$. By changing only one of the digits, there are 3 methods: $2 \times(9)=18$, (3) $\times 6=18, 2 \times 6=12$. By changing the order of $A, B, C, D$, we get $2 \times 8=16$,
$$
\therefore A+B+C+D=2+6+1+8=17 \text {, }
$$

Therefore, the answer is 17.