To find the total distance traveled by the class, you simply add the distance traveled by train to the distance traveled by bus.
Distance traveled by train: 54.6 kilometers
Distance traveled by bus: 3.9 kilometers
Total distance = Distance by train + Distance by bus
Total distance = 54.6 km + 3.9 km = 58.5 km
Thus, the class traveled a total of 58.5 kilometers.