A car travels first 160 km at 70 km/hr and the next 160 km at 80 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) 74.66  E) 71.13
Car travels first 160 km at 70 km/hr   Time taken to travel first 160 km = distancespeed=160/70   Car travels next160 km at 80 km/hr   Time taken to travel next 160 km = distancespeed=160/80   Total distance traveled = 160+160=2×160   Total time taken = 160/70+160/80   Average speed = Total distance traveled/Total time taken=320/(160/70+160/80)=74.66 km/hr   Answer:74.66
<result>D</result>
A car travels first 160 km at 70 km/hr and the next 160 km at 80 km/hr. What is the average speed for the first 320 km of the tour?