Starting at home, Luis traveled uphill to the gift store for 50 minutes at just 6 mph. He then traveled back home along the same path down hill at a speed of 12 mph. What is his average speed for the entire trip from home to the gift store and back?
Distance between home and store L = 6mph*(5/6)h = 5m
Total distance travelled = 10m
Time for return trip = 5m/(12mph) = 5/12h
Total time = (5/6)h + (5/12)h = 15/12h = 5/4h
Average speed = Total distance/Total time = 10m/(5/4h) = 40/5mph = 8mph
