Answer:
The train travelled 10hours.
Explanation:
Using speed= distance/time ...eq1
Let the time taken by train to cover the journey be t.
Let the speed of train be s
Time= distance/speed ...eq2
Time t =600/s ...eq3
The train is delayed for 1 1/2 hours=3/2 hours
Train increased by 15km/hr.
Train travelled 1/4 of 600k.= 150km.
Speed increased by s + 15 to cover the remaining 450km
t = 150/s + 400/(s + 15) + 3/2 ..eq4
Equating eq3 and 4
600/s= 150/s + 460/(s + 15) + 3/2
450/s = 3/2 + 450/(s + 15)
3s^2 + 45s -13500=0
Solving the quadratic equation
S= -45 +-sqrt(45^2-4(3×13500)/2×3
S= 60 , -75
Hence speed of train is 60km/hr
Using eq 2 distance/speed=time
600/60=10
t= 10hours
