Answer:
(96/5) mph, or 19.2 mph
Step-by-step explanation:
Average speed = (total distance traveled) / (total time elapsed)
Here we need to calculate the two elapsed times (going and returning)
Going: t1 = d/(24 mph)
Returning: t2 = d/(16 mph)
Less time is required for the outward bound trip.
16d + 24d
Total time elapsed: t = t1 + t2 = d/24 + d/16 = ------------------- = (5/48)*d hr
16*24
Thus, the average speed is (total distance traveled) / (total elapsed time)
2d
which here is --------------------- = (96/5) mph, or 19.2 mph
(5/48)d
