You are travelling at a constant speed along a road. There are 5 sets of traffic lights along this road, and they all start their sequence at the same time as you pass the zero mile marker.

At what speed do you need to travel in order to remain at your constant speed?

traffic light 1 at 3 miles is red for 36 secs and green for 22 secs.
traffic light 2 at 4 miles is red for 28 secs and green for 40 secs.
traffic light 3 at 6 miles is red for 41 secs and green for 17 secs.
traffic light 4 at 7 miles is red for 62 secs and green for 15 secs.
traffic light 5 at 9 miles is red for 46 secs and green for 25 secs.

Note, the speed is an integer, above 25 and below 100MPH.

The speed of 47 mph is the only integer speed possible to be maintained to reach each light while it is green in the mile per hour units between speeds 25 and 100 mph.

The 1st light is reached after approximately 229.79 seconds.
The light has been green for approximately 19.79 seconds of one of its '36-second red + 22-second green' cycles.

The 2nd light is reached after approximately 306.38 seconds.
The light has been green for approximately 6.38 seconds of one of its '28-second red + 40-second green' cycles.

The 3rd light is reached after approximately 459.57 seconds.
The light has been green for approximately 12.57 seconds of one of its '41-second red + 17-second green' cycles.

The 4th light is reached after approximately 536.17 seconds.
The light has been green for approximately 12.17 seconds of one of its '62-second red + 15-second green' cycles.

The 5th light is reached after approximately 689.36 seconds.
The light has been green for approximately 4.17 seconds of one of its '46-second red + 25-second green' cycles.

Posted by Dej Mar on 2008-06-29 11:40:50