A man on tour travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. The average speed for the first 320 km of the tour is :  Options.
A) 45.30 km/hr	B) 55.15 km/hr	C) 70.15 km/hr	D) 71.11 km/hr	E) None
Sol.   Total time taken = [160/64 + 160/8] hrs = 9/2 hrs.   ∴ Average speed = [320*2/9] km/hr = 71.11 km/hr.   Answer 71.11 km/hr
<result>D</result>
A man on tour travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. The average speed for the first 320 km of the tour is :