Question 352578
let the length of field be x km
Total distance it flew = 4x km
total time taken = x/200 +x/400 + x/600 + x/800
LCM = 2400
Total time = 12x+6x+4x+3x /2400
= 25x/2400  hours
...
Average speed = total distance / total time
4x / (25x/2400)
Average speed = 4x*2400/25x
=4*96 
= 384 km/h ...
m.ananth@hotmail.ca