An aeroplane flies at 800km/h for one third of its flight time and averages 700 km/h for the entire trip. What is the average speed, in kilometres per hour, over the remaining part of the journey?

Question

An aeroplane flies at 800km/h for one third of its flight time and averages 700 km/h for the entire trip. What is the average speed, in kilometres per hour, over the remaining part of the journey?
A. 600
B.750
C.650
D.500
E.625
Could you please explain in detail thank you

Steve · Answer

distance=speed*time So, if it flew at 800km/hr for x hours, then it flew at some unknown speed s for 2x hours: 800x + s*2x = 700*3x 800+2s = 2100 2s = 1300 s = 650