At 2.5 hrs into a 500 mile race a driver has an average of 190 miles per hourHow fast must he average for the remainder of the race to average 200 miles per hour?

190 mph for 2.5 hours = 475 miles. He has 25 miles to go.

200 mph for 500 miles is 2.5 hours.

Since he has reached the end of his time it means he has to drive the remaining 25 miles in zero time or at infinite speed to arrive at the finish line right now.