9. (12 points) Optimus Prime and Bumblebee start from locations $A$ and $B$ respectively at the same time, heading towards each other. When they start as robots, their speed ratio is 4:3. After they meet, they transform into Autobots, with Optimus Prime's speed increasing by $25\%$ and Bumblebee's speed increasing by $30\%$. When Optimus Prime reaches location $B$, Bumblebee is still 83 kilometers away from location $A$. What is the distance between $A$ and $B$ in meters?
【Solution】Solution: $4 \times(1+25 \%) : 3 \times(1+30 \%)$
$$
\begin{array}{l}
=5: \frac{39}{10} \\
=50: 39 \\
83 \div\left(\frac{4}{4+3}-\frac{3}{4+3} \times \frac{39}{50}\right) \\
=83 \div\left(\frac{4}{7}-\frac{117}{350}\right) \\
=83 \div \frac{83}{350} \\
=350 \text { (km) }
\end{array}
$$

Answer: The distance between $A$ and $B$ is 350 km.
The answer is: 350.