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 the correct option:
A) 70.24km/hr	B) 74.24km/hr	C) 71.11km/hr	D) 72.21km/hr	E) 75.32km/hr
Explanation:   Average Speed =2x64x80 / 64+80   =71.11km/hr   Answer is 71.11km/hr
<result>C</result>
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?