Question

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

Answer 1

hope this answer above will help you...

Answer 2

A =======B================C

Let AC is the length of railways track
e.g AC = 200 km
and AB = 50 km ,
Let speed of train for covered rest 150 km = P km/h
we know,
average speed = total distance /total time
total distance = 200 km
and averge speed = 60 km/h
total time = ?

total time = 200/60 hours = 10/3 hours
now,
time taken to cover first 50 km with 40 km/h = 50/40 = 5/4 hours .

so, time taken by train to cover next 150 km with P km/h = total time - time taken by train to cover first 50 km
= 10/3 - 5/4 = 25/12 hours

so, speed of train in next 150 km = 150/(25/12) = 150 × 12/25 = 72 km /h