Ok so we know it took 4 hrs and 15 minutes, which is the same as 4.25 hrs so we divide 1114 by 4.25 which is 262.118. The average speed of the plane is 262 mph.
Then we just have to multiply 262 by 1.6 to get the speed in kph. That equals 419.2. That means the average speed was 419 kph. Hope that helps!