Question

a bus travels the first 20 km of its journey at a uniform speed of 40 km per hour the next 45 km at a uniform speed of 60 km per hour and the last 30 km at a uniform speed of 45 km per hour calculate the average speed of the bus for its entire jorney

Answer 1

For first 20km:
Time=distance/speed
T1=20/40sec =0.5 sec.
For 45km:
T2=45/60 sec=0.75 sec.
For last 30km:
T3=30/45sec=0.66sec.
Average speed=total distance/ total time=20km+45km+30km/0.5s+0.75s+0.66s
=95/1.91
=49.7km/h