Final answer:
Mark would take 40 minutes to run 4 miles at an average speed of 6 miles per hour.
Step-by-step explanation:
To convert miles per hour to minutes per mile, divide 60 by the speed in miles per hour. In this case, Mark is running at an average speed of 6 miles per hour, so it would take him 60/6 = 10 minutes to run 1 mile.
To find out how many minutes it would take him to run 4 miles, multiply the time it takes to run 1 mile (10 minutes) by the number of miles (4). So, Mark would take 10 * 4 = 40 minutes to run 4 miles at an average speed of 6 miles per hour.