Two electric toy cars, A and B, set off at the same time from both ends of AB, which are 100cm apart, and return immediately when they arrive at either end B or A, and run back and forth. how many times.
甲乙两辆电动玩具车分别从相距100cm的AB两端同时出发，到达B端或A端立即返回，往返运行，两车的速度分别是每秒20cm和每秒10cm，问10分钟内他们一共相遇多少次．
<result>90</result>