标题: 一道数学题的讨论 [打印本页] 作者: sxu0501 时间: 2016-11-21 13:50 标题: 一道数学题的讨论 各位大神们，
遇到一个数学题，完全蒙了。请问怎么解？
Traffic light A are green for 40 sec, and then turn yellow for 5 sec, before turing red for 45 sec.
Traffic light B are gree for 35 sec, and then turn yellow for 5 sec, before turing red for 35 sec.
Both of these two sets of traffic lights have just turned green after being red. The next time when traffic light A and B change from red to green at the same time will be _____ second later?