Answer: If a car travels 300 km in 3 hours, then it’s speed will will be 100 km/hr. But in practical it depends upon type of car, condition of car, car's maximum speed and also the path in which car is travelling.. Because car can't travel in constant speed of 100 km/hr. So, if car have 120 km/hr as maximum speed than it's minimum speed will be 85–95 km/hr. And so the car travel 300 km in around 5 or 5 and half hours.