A reasonable estimate is an educated guess made by an observer based on that person's current knowledge and following observations. For example, If Garth knew that he was 1.2 meters tall, and he observed that the door was approximately twice his own height, Garth could then make the reasonable estimate that the door is about 2.4 meters tall.
The charter bus will take 7 hours to get there, so they will get there at 1pm. Her parents would actually get there before the bus because it's only going to take 5 hours.
