Answer: his average speed for the entire trip from home to the gift store and back is 14.99 mph.
Explanation:
Starting at home, Omar traveled uphill to the gift store for 30 minutes at just 10 mph. Converting 30 minutes to hours, it becomes 30/60 = 0.5 hours
Distance = speed × time
Distance covered in travelling uphill is
10 × 0.5 = 5 miles
He then traveled back home along the same path downhill at a speed of 30 mph. Since the distance is the same, then, time spent in travelling downhill is
Distance/speed
= 5/30 = 0.167 mph
Total distance = 5 + 5 = 10 miles
Total time = 0.5 + 0.167 = 0.667 hour
Average speed = total distance/total time
Average speed = 10/0.667 = 14.99 mph