a plane makes a trip of 5040 km in 7h flying with the wind R

a plane makes a trip of 5040 km in 7h, flying with the wind. Returning against the wind, the plance makes the trip in 9h. What is the speed of the wind?

Solution

Distance (d) equals Rate (r) times Time (t) or d=rt; r=d/t and t=d/r
let r =speed of the wind
And let s=speed of the plane in still air
With the wind: s+r=5040/7=720--------------eq1
Against the wind: s-r=5040/9=560------------------eq2
subtract eq2 from eq1:
2r=160
r=80 mph---------------------------speed of wind
from eq1
s+80=720
s=640--------------------------speed of plane in still air
CK
5040=(640+80)*7
5040=5040
and
5040=(640-80)*9
5040=5040