So the turquoise will move 2 miles in a full hour.
Explanation: If it moves 1/2 a mile in 1/4 of an hour. (15 minutes) In 2/4 of an hour (30 minutes) he will move another 1/2 of a mile. That's 1 mile. In 3/4 of an hour (45 minutes) he will move another 1/2 of a mile. That's 1 1/2 a mile. In 1 hour (4/4 of an hour) he will have moved 2 miles.