Hello, I was going back from a place about 100 km away from home and at one point the GPS I have was kind of stuck on a fix time of arrival, which later was corrected I presume. But it made me think of a problem which is the following. Suppose you are at exactly 100 Km from a place going on a straight road at a speed of 100 Km/hour. Obviously, it will take you 1 hour exactly to reach your destination. BUT : what would be your increase in speed or decrease IF , let's say you make a point every kilometer you made so far so that : It would be always 1 hour in time to reach your destination ? In other words, what is the change in speed IF at every kilometer there is always 1 hour left of driving until you reach destination. After 1 min at 100 km/hour, there is 99 kilometers left so if you need to reach destination in 1 hour you need to go at 99 km/hour. Is this a trivial problem ? My impression is that the speed would necessarly decrease to near 0 when you are 1 mm away from your home. In plain english , what is the function of the speed ? If someone has a solution, I would be glad to ear it. Best regards, Simon plouffe