20. (5 points) Person A and Person B start from points $A$ and $B$ respectively at the same time. If they walk in the same direction, A catches up with B in 30 minutes; if they walk towards each other, they meet in 6 minutes. It is known that B walks 50 meters per minute, then the distance between $A$ and $B$ is $\qquad$ meters.
【Solution】Solve: $50 \div\left[\left(\frac{1}{6}-\frac{1}{30}\right) \div 2\right]$
$$
\begin{array}{l}
=50 \div \frac{1}{15} \\
=750 \text { (m) }
\end{array}
$$

Answer: The distance between $A$ and $B$ is 750 meters.
Therefore, the answer is: 750.