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:

71.11 km/hr

Formulae for average speed:

Average speed = \(\frac{\text{Total distance travelled}}{ \text{Total time taken}}\)

Time taken for 1st 160 km - \(\frac{160 }{ 64}\) = 2.5 hours

Time taken for last 160 km - \(\frac{160 }{ 80}\) = 2 hours

Average speed = \(\frac{\text{160 + 160}}{ \text{2.5 + 2}}\)

Average speed = \(\frac{\text{320}}{ \text{4.5}}\)

Average speed = 71.11 km/hr