The speed ratio of the two trains is 5:4. Train B starts first, and then goes from station B to station A. when it arrives at the place 72 km away from station B, train a leaves from station a For station B, the distance between the two trains and station a and station B is 13:4, and ab distance is calculated

The speed ratio of the two trains is 5:4. Train B starts first, and then goes from station B to station A. when it arrives at the place 72 km away from station B, train a leaves from station a For station B, the distance between the two trains and station a and station B is 13:4, and ab distance is calculated

Where the two trains meet, the distance ratio between a and B is 3:4,
In the whole process of Bank A: 3 ÷ (3 + 4) = 3 / 7
B: 1-3 / 7 = 4 / 7
When B and a go at the same time, B can: 3 / 7 × 4 / 5 = 12 / 35
B: 4 / 7-12 / 35 = 8 / 35
AB distance is: 72 △ 8 / 35 = 315 km

The speed ratio of train a and B is 3:2. Train B starts first and goes from station B to station A. when it is 28 kilometers away from station B, train a goes from station a to station B,
The distance ratio between the two trains and ab station is 4:5. How many kilometers is the distance between ab station and ab station?

From car a to two cars meeting, the time is the same, distance ratio = speed ratio = 3:2
So in this period of time, the distance of B is 2 / 3 of a's
The total distance of B is 5 / 4 of A
Therefore, the distance of line a is 28 (5 / 4-2 / 3) = 48 km
So the distance between the two stations is 48 △ 4 × (4 + 5) = 108 km