An aero plane moves 400m towards north, 1200m towards east and then 300m vertically upwards. Then its displacement from initial position is

Since displacement is a vector quantity the given data can be written as S¯=1200i^+400j^+300k^ Where i^,j^&k^ are the unit vectors along east, north & upward directions (or) X-axes, Y-axes and Z-axes respectively.  Magnitude of S¯ is |S|=(1200)2+(400)2+3002=100122+42+32=100144+16+9=100169=1300m