A train takes 3.6 hours to travel a fixed route at 50 kilometres per hour. How long would that route take at 75 kilometres per hour?

Explication

The route length is 50 times 3.6, or 180 kilometres, and 180 divided by 75 gives 2.4 hours. A result of 5.4 hours scales time directly with speed, although travelling faster over the same route must shorten the journey.