Answer:
rate of the wind: 40 mph
The expression that represents the time it takes the plane to travel the 640 miles with the wind is: 640/(120 + w
)
Step-by-step explanation:
The plane fly at 120 mph. Let's call w, the rate of the wind.
Against the wind the speed of plane will be = 120 - w
With the wind the speed of plane will be = 120 + w
Speed is defined as: speed = distance/time
Time required to travel 320 miles against the wind:
time = 320/(120 - w
)
Time required to travel 640 miles with the wind:
time = 640/(120 + w
)
Both times are equal, then:
320/(120 - w
) = 640/(120 + w
)
(320/640)*(120 + w
) = 120 - w
60 + 0.5*w = 120 - w
1.5*w = 60
w = 60/1.5 = 40 mph
