Answer:
[tex]4,000\text{ miles}[/tex]
Step-by-step explanation:
Let's say that the two planes travel at point [tex]p[/tex]. Without loss of generality, let's say that the first plane travels left and the second plane travels right.
Distance is given by [tex]d=rt[/tex], where [tex]r[/tex] is rate or speed and [tex]t[/tex] is time.
If the first plane travels at a speed of 320 mph and the second plane travels 1.5 times this, the second plane must travel [tex]320\cdot 1.5=480[/tex] mph.
Using [tex]d=rt[/tex], the first plane must travel:
[tex]d=320\cdot 5=1600[/tex] miles
The second plane must travel:
[tex]d=480 \cdot 5=2400[/tex] miles
However, these are the planes' respective distances from point [tex]p[/tex]. Since they travelled in opposite directions, the total distance between them is equal to [tex]1600+2400=\boxed{4,000\text{ miles}}[/tex]
