Question

A covers 40km by 60kmph and 60km by 40kmph,find the average speed?

Answer 1

Average Speed = 60 + 40 / 2
                          = 100/2
                          = 50kmph

Answer 2

A covers 40km by 60kmph
time taken = 40/60 = 2/3 hr
A covers 60km by 40kmph
time taken = 60/40 = 3/2 hr
total time taken = 2/3 + 3/2
                           = 13/6 hr
total distance = 40+60 = 100 km
average speed =  total distance /total time
                           = 100 / 13/6
                           = 600/13
                           = 46.154 km/hr