Answer:
[tex]V_{E} = -22.5 / 15 = 1.5 miles/minute\\V_{F} = 7.5 / 15 = 0.5 miles/minute[/tex]
Step-by-step explanation:
To answer this problem, we must bear in mind that the express train travels 3 times faster than the freight train.
If we call F the distance that the freight train travels and we call E at the distance that the express train travels, we must have the distance between them after 15 minutes it must be 30 miles.
So
[tex]F + E = 30\\[/tex]
We also know that:
[tex]E = 3F[/tex]
Since the express train travels 3 times faster than the freight train.
So, like both equations, we have to:
[tex]F + 3F = 30\\F = 30/4\\F = 7.5 miles\\[/tex]
Then [tex]E = 7.5*3 = 22.5[/tex] miles in the opposite direction.
This is the distance you traveled in 15 minutes.
Therefore, the speed of the express train ([tex]V_{E}[/tex]) is the distance traveled between the time it did
[tex]V_{E} = -22.5 / 15 = 1.5 miles/minute\\V_{F} = 7.5 / 15 = 0.5 miles/minute[/tex]