Question

A weather plane took to the skies to measure the speed of the jet stream. The plane flew 1920 km with the jet stream as a tail wind. Then, it returned to its original location. The eastbound flight took 2 hours, and the westbound flight took 3.2 hours.
Which system of equations can be used to find the speed of the jet stream and the speed of the plane? What was the speed of the jet stream? (p = plane, w = wind)

A) p + w = 960; p - w = 600; jet stream's speed = 180 km/h
B) p + w = 960; p - w = 500; jet stream's speed = 180 km/h
C) p - w = 960; p + w = 600; jet stream's speed = 200 km/h
D) p + w = 960; p - w = 600; jet stream's speed = 160 km/h

Answer 1

For this case, the first thing we must do is define variables:
 p: plane speed
 w: wind speed
 With the wind in favor, the speed is:
 $p + w = 1920/2$
 With the wind against the speed is:
 $p - w = 1920 / 3.2$
 Rewriting both equations, we have the following system of equations:
 $p + w = 960 p - w = 600$
 Then, solving the system of equations (graphically for example), we have the solution is: 
 $p = 780 w = 180$
 Therefore, jet stream's speed:
 $w = 180 km / h$
 Answer:
 A) p + w = 960; p - w = 600; jet stream's speed = 180 km / h