a train travels a 20 km. at a uniform speed of 60 km/hr. and next 20 km. at a uniform speed of 80km/hr. Calculate the average speed of

Answer 1

time for slow part = 20 km/(60 km/h) = 1/3 hrs
time for faster part = 20 km/(80 km/h) = 1/4 hrs

total time = 1/3 + 1/4 hrs or 7/12 hrs
total distance = 40 km

avg speed
= total distance/total time
= 40 km/(7/12 hrs)
= appr 68.6 km/h