have 60 minutes divided by 20.3 minutes to find the correct ratio to find themph if the speed remained constant. It is about 2.95567 and using this number multiply to 21 to get the miles per hour. the speed is about 62.069 mph. then divide the 504 miles by the mph of the car to find how long it will take to get there. It is about 8 hours 7 minutes and 20 seconds give or take, or 8.12 hours.