Question 511715
The ground speed = air speed + or - the wind speed.
The wind is 30 km/h from west to east.
When the airplane is flying west, the wind is a headwind, reducing the ground speed.
When the airplane is flying east, the wind is a tailwind, increasing the ground speed.
d = r*t is the distance equation
d = 300 km
going west, ground speed = 300 km/h airspeed - 30 km/h headwind = 270 km/h
going east, ground speed = 300 km/h + 30 km/h tailwind = 330 km/h
Time (t) is the unknown.
d/r = t
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Going east...
300/(300+30) = 300/330 = 30/33 =10/11 hr 
10/11 hr * 60 min/hr = 600/11 min = approximately 54.54 min
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Going west...
300/(300-30) = 300/270 = 30/27 = 10/9 hr
10/9 hr * 60 min/hr = 600/9 = 200/3 = about  66.67 min
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Answer: The total trip takes 600/11 + 600/9 min, which equals approximately 121.21 min.
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You can check the answer to determine the distances covered each way.
10/11 hr * 330 km/hr = 300 km
10/9 hr * 270 km/hr = 300 km
Correct
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Done.