speed = distance/time
distance = speed * time
d = st
time up the mountain: t
time down the mountain: 6.6 - t
distance each way: d
Up the mountain:
d = st
d = 80t
Down the mountain
d = st
d = 85(6.6 - t)
The distances are equal, so
80t = 85(6.6 - t)
80t = 561 - 85t
165t = 561
t = 3.4
6.6 - t = 6.6 - 3.4 = 3.2
It takes 3.4 hours up the mountain and 3.2 hours down the mountain.
3.4 hours at 85 mph covers the same distance as 3.2 hours at 85 mph.
3.4 hours * 80 mph = 272 miles
3.2 hours * 85 mph = 272 miles
