Let "d" be one way distance, in miles. Then the total distance was 2d, while the total time was 9+4 = 13 hours. The average rate of 40 mph is the total distance 2d divided by the total time 13 hours. Therefore, your equation is 40 =. From the equation, 2d = 40*13, d = = 20*13 = 260 miles. ANSWER. One way distance is 260 miles long.