Question

a car travel half of the distance with 40 km per hour velocity and half by 50 km per hour ,so what time required to travel whole distance??

Answer 1

Let x be the distance travelled by the car..x/2 be half the distance now time t taken by the car with a velocity 40km/hr is x/80hr (time=distance/speed) time t taken by the car with a velocity 50km/hr is x/100 hr. 
now avg velocity= x/2+x/2
                           x/80+x/100

                          = x*8000
                                180x

                           = 44km/hr