A car travels first 160 km at 75 km/hr and the next 160 km at 90 km/hr. What is the average speed for the first 320 km of the tour?	Pick: A) 71.11 B) 71.12 C) 71.1 D) 71.17 E) 81.81

Rationale: "car travels first 160 km at 75 km / hr time taken to travel first 160 km = distancespeed = 160 / 75 car travels next 160 km at 90 km / hr time taken to travel next 160 km = distancespeed = 160 / 90 total distance traveled = 160 + 160 = 2 × 160 total time taken = 160 / 75 + 160 / 90 average speed = total distance traveled / total time taken = 320 / ( 160 / 75 + 160 / 90 ) = 81.81 km / hr answer : e"
Answer: E