The circumference you found in part A is in inches. To convert the circumference to miles, divide the number of inches by 12 to get the circumference in feet. Then divide that number by 5,280 (there are 5,280 feet in a mile) to get the circumference in miles. This number is the number of miles a cup traveled in one revolution. Multiply this value by the 150 revolutions the cup made in one minute. Then multiply by 60 minutes to get the approximate number of miles per hour. Note: This is only an approximate value because it does not take friction into account.