A car moves with a constant speed 60 km / hr for 1 km and 40 km / hr in next 1 km what is the average speed of car?

Solution :

For first 1 km

Speed is 60 km / hr        =       60/3600 km / sec

                                      =       ( 1 / 60 ) km / sec

                                      =       0.01666 km / sec

We know that,

V = distance / time

Therefore,

Time = distance / velocity

Time =        1 / 0.01666 =       60 sec

Therefore car takes 60 seconds to cover first one km

For next 1 km

For first 1 km

Speed is 40 km / hr        =       40/3600 km / sec

                                      =       ( 1 / 90 ) km / sec

                                      =       0.01111 km / sec

We know that,

V = distance / time

Therefore,

Time = distance / velocity

Time =        1 / 0.1111   =       90 sec

Therefore car takes 900 seconds to cover another one km.

Total distance cover by car is  2 km in time ( 60 + 90 = ) 150 sec.

The Average speed is

V_a = ( Total distance travel ) / (Time)

V_a = 2 / 150

V_a = 0.01333 km / sec

V_a = 0.01333 X 3600 km / hr

V_a = 48 km / hr

Therefore the average speed of car is 48 km / hr