It takes Joey the postman 1 hours to run a 5 mile long route every day. He delivers packages and then returns to the post office along the same path. If the average speed of the round trip is 8 mile/hour, what is the speed with which Joey returns?  Options:  A) 11  B) 12  C) 13  D) 14  E) 20

Rationale: let his speed for one half of the journey be 5 miles an hour let the other half be x miles an hour now , avg speed = 8 mile an hour 2 * 5 * x / 5 + x = 8 10 x = 8 x + 40 = > 2 x = 40 = > x = 20 e
Answer: E