1hr=60mins
1min=60seconds
1hour=60*60=3600seconds
ratio and proportaion
distance/time=distance/time
39/7=x/3600
times both sides by (7*3600)
140400=7x
divide both sides by 7
20057 and 1/7=x
answer is 20057 and 1/7 meters per hour
or
20.0571428km per hour
