Question

A train travel 20 km at a uniform speed of 60 km/ h and the next 20km at a uniform speed of 80 km /h calculate the average speed

Answer 1

case 1

distance=20km
speed=60km/hr
case 2
distance=20km
speed=80km/hr

so average speed is : 140/40
=14/4
3.5 is the average speed

Answer 2

20/60=0.33hr
20/80=0.25hr
Total time=0.58hr
Avg. Speed=40/0.58
68.96km/h