<PRE><B>Question 176004</B>
Flying against the jetstream, a jet travels 2920km in 4 hours. Flying with the jetstream, the same jet travels 7630km in 7 hours. What is the speed of the jet in still air, and what is the speed of the jetstream? 
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2920 km/4 hrs = 730 kph ground speed
7630 km/7 hrs = 1090 kph ground speed
The airspeed of the plane is the average, (730+1090)/2
Airspeed = 910 kph
The wind speed is the difference between either groundspeed and the airspeed.
910 - 730 = 180 kph wind speed.
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BTW, kilometers and kph are not used in aviation, we use nautical miles and knots.  1 knot is 1 nm/hour.
Flying with the wind is called downwind, or flying with a tailwind.  Against it is called upwind, or into a headwind.
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