Question

On a 200m track, a train travels the first 50km at a uniform speed of 40km/h. How fast the train must travel the next 150km so as to maintain the average speed of 60km/h for the whole journey

Answer 1

Answer:

it have to travel next 150 km with a speed of 72 kmph

Answer 2

Answer:

72 km / hr

Explanation:

let speed in the next 150 km be x km/hr for first 50 km, speed = 40 km/hr so time taken = 50 / 40 = 5/4 hr for the next 150 km, speed = x so time taken = 150/x hr total time = 5/4 + 150/x = (5x + 600) / 4x hr average speed = total distance / total time or 200 / [(5x + 600) / 4x] = 60 or (200 * 4x) / (5x + 600) = 60 or 800 x = 60 * (5x + 600) or 800x = 300x + 36000 or 500x = 36000 or x = 36000/500 = 72 km/hr