A man on tour travels first 160km at 64km/hr and the next 160km at 80km/hr. The average speed for the first 320km of the tour is?  Choose the correct choice from the following:  A) 56.45km/hr  B) 71.11km/hr  C) 68.78km/hr  D) 75.63km/hr  E) 66.56km/hr
Total time taken = 160/64 + 160/8 = 9/2 hrs   Average speed = 320*2/9 = 71.11km/hr   Answer is 71.11km/hr
<result>B</result>
A man on tour travels first 160km at 64km/hr and the next 160km at 80km/hr. The average speed for the first 320km of the tour is?