Mega-Runners Running on a Mega-Track

When the first meet, it will look like the start except in a different location. Both people will be running in opposite directions at the same speed.

So now we need to figure out how many kilometers the runner who ran a lap in $5$ minutes will run before the next meeting. The ration of the speed of the first runner to the second runner is $5:4$ , meaning the first runner is $\frac{5}{4}$ times faster than the second runner.

So when the first runner will travel $\frac{5}{5+4}$ , or $\frac{5}{9}$ of the track, the second runner will run $\frac{4}{9}$ of the track.

$\frac{4}{9}$ of $720$ kilometers is $320$ kilometers. So now we can convert this into meters by multiplying by 1000.

This gives us an answer of $\boxed{320,000}$ meters.