A girl walks 4 km towards west, then she walks 3 km in a direction 30° east of north and stops. Determine the girl’s displacement from her initial point of departure.
let O be the initial position and B be the final position of the girl.
Position of girl will be as shown in figure:
Hence, 
and ∠ BAO = 60°
Now, by using triangle law of vector addition,
Hence girls displacement from initial to final position is : 
4