Starting at home, Omar traveled uphill to the gift store for 3 0 30 minutes at just 1 0 10 mph. He then traveled back home along the same path downhill at a speed of 3 0 30 mph. What is his average speed for the entire trip from home to the gift store and back?

15 mi/h

Step-by-step explanation:

In 1/2 hour at 10 mi/h, Omar covered 5 miles, the distance to the store. At 3 times the speed (30 mi/h), he covered the same distance in 1/3 the time on the way home: 1/6 hour.

His total distance was 2· (5 mi) = 10 mi.

His total time was (1/2 h) + (1/6 h) = 2/3 h.

speed = distance/time

His average speed was (10 mi) / (2/3 h) = 15 mi/h.