posted by Matt .
A family drove 1080 miles to their vacation lodge. Because of increased traffic density, their average speed on the return trip was decreased by 6 miles per hour and the trip took 2.5 hours longer. Determine their average speed on the way to the lodge.
since time = distance/speed,
1080/s + 5/2 = 1080/(s-6)
s = 54
So, speed out = 54, sped back = 48
2160/(1080/54 + 1080/48) = 50.8 mph avg speed