17. Person A and Person B start from points $A$ and $B$ respectively at the same time, heading towards each other. When A reaches the midpoint $C$ between $A$ and $B$, B is still 240 meters away from $C$. When B reaches $C$, A has already passed $C$ by 360 meters. Then, when the two meet at point $D$, the distance $CD$ is $\qquad$ meters.
【Analysis】From the known conditions in the problem, derive the speed ratio of A and B, and then derive their distance ratio. This way, we can find the distance A travels after reaching the midpoint and then traveling 240 meters with B, which is the distance between $C D$.

【Solution】Solution: From the problem, we know that "when A walks 360 meters, B exactly walks 240 meters," the speed ratio of A and B is 360: 240 $=3: 2$.

In the same amount of time, the distance ratio of A and B equals their speed ratio, which is 3: 2.
When A and B travel 240 meters together, the distance A travels is $240 \times 3 \div (2+3)=144$ (meters).
Therefore: The distance between $C D$ is 144 meters.
【Comment】The key to solving this problem is to derive their speed ratio, after which the solution becomes straightforward.