Question

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:

Answer 1

Total time taken =( 160/64 + 160/80 )= 9/2 hrs

average speed = 320 * 2/9 = 71.11 km/hr

Answer 2

A man covered 160 km with speed 64km/h.

hence, time taken by man to cover 160km = 160/64 hrs = 5/2 hrs

again, man covered next 160 km with speed 80km/h

hence, time taken by man to cover next 160 km = 160/80 = 2 hrs

now,

average speed = total distance/total time taken

= ( 160 + 160) km /( 5/2 + 2)hrs

= 320/(9/2) km/h

= 320×2/9 km/h

= 71.11 km/h

hence, average speed = 71.11 km/h