Rohit travelled 120 km in a train running at a speed of 60 km/h and further he travelled for 20 minutes in a bus and covered 13 km. His average speed for the entire journey (in km/h) is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 57
Average speed is total distance divided by total time, not the average of the two speeds, because the two parts of the journey take different times.
Time in the train: \(\displaystyle\frac{120}{60}=2\) h
Time in the bus: 20 min \(\displaystyle=\frac{1}{3}\) h
Total distance: \(120+13=133\) km
Total time: \(\displaystyle2+\frac{1}{3}=\frac{7}{3}\) h
Average speed \(\displaystyle=133\div\frac{7}{3}=133\times\frac{3}{7}=57\) km/h