Question

The distance between Delhi and Agra is 200km a train travels the first 100km at speed of 50km/h how fast must the train travel next 100km so that the average speed is 70km/h for the whole journey​

Answer 1

Answer:

Time taken to travel first half distance = 100/ 50 = 2 hrs

Time is taken to travel second half distance = 100/v

Average speed = 200/ (2 + 100/v)

70 = 200/ (2 + 100/v)

2 + 100/v = 20/7

100/v = 20/7 – 2 = 6/7

v = 100 * 7/6 Km/h

v = 700/6 km/h

Answer 2

Answer:

Time taken to travel first half distance = 100/ 50 = 2 hrs

Time is taken to travel second half distance = 100/v

Average speed = 200/ (2 + 100/v)

70 = 200/ (2 + 100/v)

2 + 100/v = 20/7

100/v = 20/7 – 2 = 6/7

v = 100 * 7/6 Km/h

v = 700/6 km/h