The distance between 2 stations A and B is 160 km.A train covers first 40 km at a speed of 20 km/hr.How fast a tain travel while covering the remaining distance , so that its average speed for the whole trip is 40 km/hr ?

Asked by nisha_vini29 | 1st Jul, 2017, 10:00: AM

Expert Answer:

- For an average velocity 40 km/hr to cover the total distance of 160 km, the total time of travel should be,
begin mathsize 12px style Speed equals Distance over Time
Time equals 160 over 40 equals 4 space hours end style
- Time taken by the train to cover the first 40 km at the speed of 20 km/hr is,
begin mathsize 12px style Time equals Distance over Speed equals 40 over 20 equals 2 space hours end style
- Now, the remaining distance of 120 km should be covered in 4-2= 2 hours, so that the total average velocity of the train is 40 km/h.
- Speed of the train while covering the remaining distance of 120 km in 2 hours is,
begin mathsize 12px style Speed equals Distance over Time equals 120 over 2 equals space 60 space km divided by hr end style.
- Therefore, the train should travel at a speed of 60 km/hr while covering the remaining distance, so that its average speed for the whole trip is 40 km/hr.
          

Answered by Abhijeet Mishra | 2nd Jul, 2017, 02:22: PM