求救阿各位数学神人老师

othernetwork

在大学上课遇到一个将的问题...
请帮忙解答
真的太太太太难了！！

There were some traffic lights on the way from John's house to his office. The distance between each traffic light was 450 meters. Each traffic light functions in a following pattern, 35 seconds of green light followed by 5 seconds of yellow lights followed 35 seconds of red light. One morning, John was riding this motorcycle to his office at the speed of 54 km/hr. He found that at each junction he met the green light. If he used the same way to go back from his office to his house, what is the maximum speed at which he should ride in order to make sure that he will meet the green light at all the junctions. (except the first one).

ywhterry

我来试试：

先解决去office的路线：
1. 没有说有多少个红绿灯。所以：当他到下一个红绿灯的时候，红绿灯的显示状态一定要跟前面的一样，例如：第一个灯是刚刚绿灯，当他去到下一个灯的时候一定也要刚刚绿灯。
2. 450m距离，54km/h需要30秒到下一个灯。

结论：每一个灯都要比前一个灯慢30秒。

回程：
1. 如果说来office每个灯都慢30秒，那回程每个灯都会比前面的灯快30秒/慢45秒。
2. 例子：第一个灯如果是红灯，当他等到绿灯的时候，下一个灯已经剩5秒绿灯了。
3. 450m距离，需要45秒来完成，所以速度是10m/s。

结果：36km/h