Average speed and pace from a distance and a time.
Divide the distance by the average speed. Two hundred kilometres at ninety km/h is 2.22 hours — two hours and thirteen minutes. The answer comes out in decimal hours, so multiply the fraction by sixty to get minutes.
Because an average includes everything: built-up areas, junctions, stops and refuelling. On Latvian highways with a ninety km/h limit, the real average over a long trip is usually seventy to eighty.
Less than it feels. A hundred kilometres at ninety takes 66.7 minutes; at a hundred it takes 60 — under seven minutes saved. Fuel use rises at the same time, because drag grows with the square of speed.
Divide the distance by the time left in hours. With 120 kilometres to go and an hour and a half remaining, you need an average of 80 km/h. If the number comes out above the speed limit, the only honest answer is to warn that you will be late.