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?

So her average speed for the entire trip is 30 mph (miles per hour).

Step-by-step explanation:

Use distance = rate x time

18 minutes is 3/10 of an hour.

So the distance to the store is:

d = 20 * (3/10) = 6 miles

The distance downhill is the same, 6 miles. So:

6 = (60) t

6/60 = t

1/10 = t

Where 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 time

average speed = (6+6) / (.3 +.1) = 12 / (.4) = 30

So her average speed for the entire trip is 30 mph (miles per hour).