Is this a genuine question? If so, you would calculate how long it would take for you to reach your destination based on the speed limit. If the speed limit is 40 mph and you need to drive 100 miles, divide the distance by the speed and you find it would take you 2.5 hours. If you speed and go, let’s say 50 mph, divide 100 miles by 50 mph and you will find that it will take 2 hours, saving half an hour of time. Use this strategy to find out how much time you save.