How to work out 6km/hr for 45minutes
More generaly if you are moving at speed of x km/h for m minutes, you will travel the path s= m/60 * x. Because formula for traveled distance is s=v/t where s is distance traveled, v is velocity and t is time. m/60 because 1h=60min.
Alternative is to change all data into coresponding units, that is minutes to hours or km/h into km/min or you can change all into standard SI units that is km/h into m/s and minutes to seconds, after wich you can aplly the formula s=v/t.
45 minutes is 3/4 of an hour so divided 6km by 3/4 which equals 4.5 km.