time speed distance

Question

Excluding stoppages the speed of a bus is 54 kmph and including stoppages it is 45 kmph for how many minutes does the bus stop per hour

 

 

in my answer book 

Due to stoppages it cover 9km less

time taken to cover 9 km =9/54*60

                                     =10 min

 

i dont understand the solution how they convert 9kmph speed into distance and also everything they solved in solution please explain me

Answer 1

In one hour, non-stop, the bus would go 54 km.

But with stops, the travel (at the 54 kph rate) is only able to cover 45 km.

So the distance lost due to stoppage(s) is equivalent to 9 km.

 

D = RT (distance = rate × time); 9 km = 54(time lost) ⇒ t = 1/6 hour; this is 10 minutes of total stoppage(s).