convert total kilometers to miles:
3 km x 0.6 miles/km = 1.8 miles
20 minutes is 1/3 of an hour so multiply the total miles by 3:
1.8 * 3 = 5.4 miles per hour ( 60 minutes)
Divide total miles per hour by 60 to get miles per minute:
5.4 miles / 60 minutes = 0.09 miles per minute.