Second part of the question is that train stops for 4 minutes after every 15 kilometers. Let us calculate total number of stops in 60 kilometers. This will be calculated by dividing total distance by 15.
So, total number of stops = 60 kilometers ÷ 15 kilometers = 4
This means that train will stop 4 times to cover 60 kilometers. One thing here to notice that after third stop, when the train runs for another 15 kilometers, then it completes its journey and there is no further move, so no need to count last stop as a valid stop point while calculating the time. Let us understand this by the diagram below:
As you can see that after 3^{rd} stop, the train finally stops after covering 15 kilometers, so we are not considering last stop as 4^{th} stop.
As the train stays for 4 minutes at one stop, so at three stop it will stay for: 3 stops x 4 minutes = 12 minutes
So, total travelling time = 1 hour 30 minutes + 12 minutes
= 1 hour 42 minutes (answer)
