6. (10 points) Car A and Car B depart from City A to City B, which is 300 kilometers away. It is known that Car A departs 1 hour later than Car B, but arrives 1 hour earlier at City B. Then, Car A catches up with Car B at a distance of $\qquad$ kilometers from City B.
【Answer】Solution: Driving 300 meters, car A is 2 hours faster than car B; so for car A to be 1 hour faster, both need to drive 150 meters; $300-150=150$ (kilometers);

Therefore, the answer is: 150