Answer:
26.5 minutes
Explanation:
When the airplane is flying due West from Denver to Reno, the due-East wind with speed of 80km/h would reduce the ground speed by 80 km/h.
Its Denver to Reno ground speed is 900 - 80 = 720 km/h
The time it takes to cover 1200km at this speed is 1200 / 720 = 1.67 hours
On the other hand, when it returns from Reno to Denver in the due-East direction, the due-East wind with speed of 80km/h would add to the ground speed by 80 km/h
Its Reno to Denver ground speed is 900 + 80 = 980 km/h
The time it takes to cover 1200 km at this speed is 1200 / 980 = 1.22 hours
The difference it flight time would be 1.67 - 1.22 = 0.44 hours or 26.5 minutes
