A plane flies 880 km with the wind and 720 km against the wind in the same length of time. If the speed of the wind is 20 km/h, what is the speed of the plane in still air? Pick: A) 140 km/h B) 160 km/h C) 180 km/h D) 200 km/h E) 220 km/h
The speed of the plane in still air = x km/h   The speed of the wind is 20 km/h   Speed with the wind = (x + 20) km/h   Speed against the wind = (x â€“ 20) km/h   Time = Distance/ Speed   880 / (x+20) = 720 / (x-20)   880(x-20) = 720(x+20)   88x - 1760 = 72x + 1440   16x = 3200   x = 200   Therefore, the speed of the plane in still air is 200 km/h.   The answer is 200 km/h.
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A plane flies 880 km with the wind and 720 km against the wind in the same length of time. If the speed of the wind is 20 km/h, what is the speed of the plane in still air?