A car travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. What is the average speed for the first 320 km of the tour? Choose one:
A) 71.11
B) 71.12
C) 71.1
D) 71.17
E) 71.13

Rationale: "car travels first 160 km at 64 km / hr time taken to travel first 160 km = distancespeed = 16064 car travels next 160 km at 80 km / hr time taken to travel next 160 km = distancespeed = 16080 total distance traveled = 160 + 160 = 2 × 160 total time taken = 16064 + 16080 average speed = total distance traveledtotal time taken = 2 × 16016064 + 16080 = 2164 + 180 = 2 × 64 × 8080 + 64 = 2 × 64 × 80144 = 2 × 8 × 8018 = 6409 = 71.11 km / hr answer : a"
Answer: A