a car journey of 560km took 6hrs and 45mins calculate the average speed for the journey in km per hour

45 mins  =  45/60 hours  =  .75 hr

6 hrs 45 mins  =  6.75 hrs

Distance  =  Rate x Time

560 kms  =  Rate x 6.75 hrs

Divide both sides by 6.75 hrs:

560 kms / 6.75 hrs  =  Rate