To a man going east in a car with a velocity of 40km/h,a train appears to move towards north with a velocity of 40√3 km/h.what is the actual velocity and direction of train ?

The relative motion of the train as seen from the car is the difference between the actual velocities of the train and car:


\vec v_{relative} = \vec v_{train} - \vec v_{car}


Rearrange:


\vec v_{train} = \vec v_{relative} + \vec v_{car}


So simply add the two vectors that you were given.