Answer:53.3m/s
Step-by-step explanation:
time for first travel
time=distance/speed
time=40/80
time=0.5seconds
time for second travel:
time=distance/speed
time=40/40
time=1seconds
total time=0.5+1
total time=1.5seconds
Then average speed for 80km trip:
Speed=distance/time
Speed=80/1.5
Speed=53.3m/s