Question

An airplane flew 3 hours with a 40 mph head wind. The return trip with a tail wind of the same speed took 2 hours. Find the speed of the plane in still air

Answer 1

We can use the formula d = rt

The first equation is

d = (x + 40)3

What did you get for the second equation?

Answer 2

We know that d=vt (d=distance, v=velocity (speed), and t=time) and also that the distance each way is exactly the same. Therefore we can set the Distances equal to each other:

D = D
Vt*time = Vh * time

(Vp+40)2 = (Vp-40)3
2Vp+80 = 3Vp -120
200 = Vp

So the speed of the plane in still air is 200mph.