Jeff takes 20 minutes to jog around the race course one time, and 25 minutes to jog around a second time. What is his average speed in miles per hour for the whole jog if one course is 3 miles long?

Jeff ' s average speed for the whole jog is 6 . 6 7 miles per hour . \n \n Here ' s the reasoning : \n \n 1 . Jeff jog s around the first course for 2 0 minutes , which is equivalent to 1 / 3 of an hour ( since there are 6 0 minutes in an hour ). \n 2 . The first course is 3 miles long . \n 3 . To calculate Jeff ' s speed for the first course , we can use the formula : speed = distance / time . So , Jeff ' s speed for the first course is 3 miles / 1 / 3 hour = 9 miles per hour . \n 4 . Jeff jog s around the second course for 2 5 minutes , which is equivalent to 5 / 6 of an hour . \n 5 . The second course is also 3 miles long . \n 6 . To calculate Jeff ' s speed for the second course , we can use the same formula : speed = distance / time . So , Jeff ' s speed for the second course is 3 miles / 5 / 6 hour = 6 miles per hour . \n 7 . To find Jeff ' s average speed for the whole jog , we can use the formula : average speed = total distance / total time . \n 8 . The total distance is 6 miles ( 3 miles for each course ). \n 9 . The total time is 1 / 3 hour + 5 / 6 hour = 1 9 / 6 hours . \n 1 0 . So , Jeff ' s average speed for the whole jog is 6 miles / ( 1 9 / 6 ) hours = 6 . 6 7 miles per hour . </s>