What was the speed of the wind, in km/hr?

Question

An aircraft with a constant speed in still air travels 4800 km with a constant tailwind in 4 hours. With the same wind now against the aircraft, it takes 5 hours to make the return trip. What was the speed of the wind, in km/hr?

a. 100

b. 110

c. 120

d. 125

e. 900

f. 990

g. 1080

h. 1125

i. none of these

I get to the point of
4800/4=1200
4800/5=960
then i don't know how to go from there

Answer 1

_______________Downwind_____Upwind
Distance (miles)_____4800_______4800
Time (h)____________4___________5
Speed (mph)_______1200________960

Let speed in still air = x mph
Let wind speed = w mph

x + w = 1200
x - w = 960

2x = 2160
x = 1080

w = 1200 - 1080
w = 120

Wind speed = 120 mph

Option c

Answer 2

If w is the speed of the wind and v is the airspeed of the plane, ground velocity r is given by
r = v + w (for the first leg)
r = v - w (for the return trip)

By the distance formula, d = rt, set up two equations, one for each leg:
4800 = 4 (v + w)
4800 = 5 (v - w)

Simplify:
4800/4 = v + w
1200 = v + w

4800/5 = v - w
960 = v - 2

Eliminate the variable v by subtracting the second equation and solve for w:
v + w = 1200
v - w = 960
——————
2w = 240
w = 120.

This gives you 120 km/h, so the answer is (C).

Answer 3

C. 120

If the plane has a tailwind and makes the trip in 4 hrs. @ 1260kph

Then, the plane has a the same windspeed in the form of a headwind now and makes the same trip in 5 hrs. @ 960kph.

The plane was helped by the tailwind at the same rate it was hampered by the headwind.

So...if the difference between the two trips was 240kph...then the wind was blowing at 120 kph.