We are given that the time record in a 1 mile run is 3:59.37 where this is in the format of HH:MM
There are 3 hours 59.37 minutes. Converting every unit to hour:
3 hours + 59.37 min (1 hour / 60 minute) = 3.9895 hour
So the average speed is:
average speed = 1 mile * (1.61 km / mile) / 3.9895 hour
average speed = 0.4 km / hour