A car can accelerate 0-60 mph in 8.6 seconds and 0-100 mph in 26.1 seconds. How far (in feet) would the car have to travel in order to accelerate from 0-81 mph?
The acceleration rate from 0-60 mph is different than the acceleration rate from 0-100 mph. You could assume that the rate of acceleration is inversely proportional to the final speed (linear), but that really isn't the case with cars. So, with the given data, this problem is not solvable. The best you can do is find an estimate.