Answer:
To find the average speed, you need to convert the time from minutes to hours and then divide the distance by the time.
Time: 30 minutes = 0.5 hours (since there are 60 minutes in an hour)
Distance: 312 km
Average Speed = Distance ÷ Time = 312 km ÷ 0.5 h = 624 km/h
So, the airplane's average speed is 624 kilometers per hour.