Final answer:
To find Jen's average speed for the round trip, we consider the total distance to be 2d and the total time to be (4d)/60 hours. Her average speed is thus the total distance divided by the total time, which calculates to 30 mph.
Step-by-step explanation:
To calculate Jen's average speed for the round trip from Boston to Cape Cod and back, we need to know the total distance traveled and the total time taken.
Let's assume the distance from Boston to Cape Cod is d miles. Since Jen traveled to Cape Cod at 60 mph, the time for the trip there is d/60 hours. On the way back, the trip took 3 times as long, so the return time is 3d/60 hours, or d/20 hours.
The total distance for the round trip is 2d miles (since she made the trip there and back), and the total time taken is d/60 + d/20 hours which adds up to (4d)/60 hours.
The formula for average speed is total distance divided by total time. Therefore, Jen's average speed for the round trip is:
Average speed = Total distance / Total time
= 2d / ((4d)/60)
= 2d / (4d/60)
= 2d * (60/4d)
= 30 mph.
Thus, Jen's average speed for the entire trip was 30 mph.