To find the required speed for the next 30 km, let's first determine the time it takes for the train to travel the first 30 km.
Time = Distance / Speed
Time = 30 km / 30 km/h
Time = 1 hour
Since the train needs to maintain an average speed of 40 km/h for the entire trip, and it has already spent 1 hour traveling the first 30 km, the remaining 30 km must be covered in the remaining time.
Remaining time = Total time - Time spent on the first 30 km
Remaining time = 60 km / 40 km/h - 1 hour
Remaining time = 1.5 hours - 1 hour
Remaining time = 0.5 hours
To find the speed required for the next 30 km, we'll use the formula:
Speed = Distance / Time
Speed = 30 km / 0.5 hours
Speed = 60 km/h
Therefore, the train must travel at a speed of 60 km/h for the next 30 km to maintain an average speed of 40 km/h for the entire trip.