Question

An express train covers the first half of its journey
in 1 h 20 min, travelling at 90 km/h. Due to heavy
fog, the next 12 km of its journey could be covered at
40 km/h. If it covers the rest of the journey in
52 minutes, find the total time taken and the average
speed of the train for the entire journey.​

Answer 1

Answer:

First half of the journey is covered by in 80 minutes at the speed of 90 km/h

So, distance covered in 1 min = 90/60=3/2=1.5 km i.e. the speed is 1.5 km/min

Therefore, the distance covered in 80 minutes = 1.5 x 80 = 120 km

First half distance is 120 km

Therefore, the total distance of the journey is 240 km

Now, 12km is covered at the speed of 40km/h i.e. 2/3 km/min

Therefore, the time taken to cover 12 km is 18 minutes

The rest of the 108 km is covered in 52 minutes.

So, total time taken is 150 miutes and total distance covered is 240 km

Therefore, the average speed of the train is 240/150 = 8/5 km/minute = 96 km/h