Starting at home, Jessica traveled uphill to the grocery store for 181818 minutes at just 202020 mph. She then traveled back home along the same path downhill at a speed of 606060 mph. What is her average speed for the entire trip from home to the grocery store and back?

Answer:So her average speed for the entire trip is 30 mph (miles per hour).Step-by-step explanation:Use distance = rate x time18 minutes is 3/10 of an hour.So the distance to the store is:d = 20*(3/10) = 6 milesThe distance downhill is the same, 6 miles. So:6 = (60)t6/60 = t1/10 = tWhere t is the time it took to go back home.  So t is .1 hour (6 minutes).To calculate average speed we use the formula:average speed = total distance/ total timeaverage speed = (6+6)/(.3 + .1) = 12/(.4) = 30So her average speed for the entire trip is 30 mph (miles per hour).