If a bus covers 40 km in 1 hour ( its doing 40 km per hour) it will take a lot more than an hour to cover 90 km eh?
It will in fact take 1 hour times the proportion that 90 has to 40 that is 90 divided by 40 times 1 hour
eg 90/40 = 2.25 times 1 hour!
The bus will take 2.25 hours to travel 90 km at 40 km per hour