Answer: plane 1: 420 mph; plane 2: 500 mph
Step-by-step explanation:
This is a physics exercise, but in order to solve this problem, you need to identify both planes first:
Let's call the plane 1 speed X
V1 = X
And V2 would be:
V2 = V1 + 80 = X + 80
If we combine both speeds:
V = V1 + V2 = X + X + 80 = 2X + 80
Now that we have an expression for the combined speed, let's see the rest of the data:
Distance: d = 1380 mile
Time: t = 1.5 h
We also know that the formula to get speed is:
V = d/t
We have the combined speed, so, let replace it in the above formula to solve for X:
2X + 80 = 1380/1.5
2X + 80 = 920
2X = 920 - 80
2X = 840
X = 840/2
X = V1 = 420 mph
We have V1, so to get V2:
V2 = 420 + 80 = 500 mph
