An airplane has enough fuel for 3 hours of safe flying. On the trip out the pilot averages 200 mph flying against a headwind. On the trip back, the pilot averages 250 mph. How long a trip out can the pilot make?
Let airplane trips out for x hours. Hence trips in = 3 - x hours.
In x hours plane trips out = 200 x km as in 1 hours it goes 200 km.
Same way (3 - X) hours plane trips in 250 (3 - x) km as in 1 hours it goes 250 km.
Now, trips out = trips in [ means plane has to go some distances and returned back also the same distances within 3 hours.]
Thereby, 200 x = 250 (3 - x)