Final answer:
To calculate the return trip time, the total outbound distance of 90 miles is divided by the motoring speed of 5 mph, resulting in 18 hours for the return trip.
Step-by-step explanation:
The question you've asked is about calculating the time it takes for a return trip when a ship motors at a different speed than when it sails. Given that the ship sails to its destination at 15 miles per hour for 6 hours, we can calculate the total distance covered during this outbound trip.
Total Distance = Speed × Time = 15 mph × 6 h = 90 miles.
For the return trip, the ship motors at a slower speed of 5 miles per hour.
Total Time for Return Trip = Total Distance ÷ Speed = 90 miles ÷ 5 mph = 18 hours.
Therefore, it will take the ship 18 hours to motor back to its starting point.