15. (6 points) A car and a truck start from locations $A$ and $B$ respectively at the same time, heading towards each other. It is known that the car's speed is twice that of the truck. The car arrives at point $C$ on the way at 8:30, and the truck arrives at point $C$ at 15:00 on the same day. The two vehicles do not stop when they reach point $C$ and continue to move forward. The time when the two vehicles meet is $\qquad$.
【Analysis】Traveling towards each other simultaneously means that the time taken to meet is the same, regardless of the starting moment. Therefore, we can consider the situation from when the car reaches point $C$ at 8:30. The time difference between the two vehicles passing point $C$ is 6 and a half hours, which is $6 \times 60 + 30 = 390$ minutes. Since the speed ratio of the two vehicles is 2:1, the distance ratio they travel when they meet is also 2:1. Therefore, the time ratio to complete this segment of the journey is 1:2. Considering the total time as a whole, the truck needs $390 \div 3 = 130$ minutes to meet the other vehicle. Thus, the meeting time should be 8:30 plus 130 minutes, which is 10:40.

【Solution】Solution: Based on the analysis of the problem:
From when the car reaches point $C$ at 8:30, the time difference between the two vehicles passing point $C$ is 6 and a half hours, which is $6 \times$ $60 + 30 = 390$ minutes;

Since the speed ratio of the two vehicles is 2:1, the distance ratio they travel when they meet is also 2:1, so the time ratio to complete this segment of the journey is 1:2;

The truck needs $390 \div 3 = 130$ minutes to meet the other vehicle, so the meeting time should be 8:30 plus 130 minutes, which is 10:40.

Therefore, the answer is: 10:40.