A plane flies 660 km with the wind and 540 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? Choose one:
A) 160 km/h	B) 180 km/h	C) 200 km/h	D) 220 km/h	E) 240 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   660 / (x+20) = 540 / (x-20)   660(x-20) = 540(x+20)   66x - 1320 = 54x + 1080   12x = 2400   x = 200   Therefore, the speed of the plane in still air is 200 km/h.   The answer is 200 km/h.
<result>C</result>
A plane flies 660 km with the wind and 540 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?