There are two signal lights A and B in the railway freight dispatching station, and three trains A, B, and C are parked beside the lights. Their lengths just form an arithmetic sequence, and the length of the second train is in the middle. At the very beginning, the rears of cars A and C are aligned, and the rear of the car is just at the signal light of A, while the front of the car is facing the direction of the signal light of B. direction. Now, the three trains start to move forward at the same time, and the fronts of the three trains just meet after 10 seconds. After another 15 seconds, car A happens to overtake car C completely, and car C happens to completely stagger with car B. May I ask: How many seconds did it take for cars A and B to meet each other at the front until they completely staggered?
铁路货运调度站有A、B两个信号灯，在灯旁停靠着甲、乙、丙三列火车，它们的车长正好构成一个等差数列，其中乙车的车长居中．最开始的时候，甲、丙两车车尾对齐，且车尾正好位于A信号灯处，而车头则冲着B信号灯的方向，乙车的车尾则位于B信号灯处，车头则冲着A的方向．现在，三列火车同时出发向前行驶，10秒之后三列火车的车头恰好相遇．再过15秒，甲车恰好完全超过丙车，而丙车也正好完全和乙车错开．请问：甲、乙两车从车头相遇直至完全错开一共用了几秒钟？
<gadget id="calculator">35 / 4</gadget>
<output>35/4 = around 8.75</output>

<result>35/4 = around 8.75</result>