Question

A boy stops after travelling 3km towards east and then goes 4km towards north along a plane road. The resultant displacement of the boy is what

Answer 1

As shown in the figure in image that the body first moves from A to B (3 km) and then to point C (4km).
As displacement is the shortest distance between two points so the displacement would be AC.
Using pythagoras theorem
(AC)^2 = (AB)^2 + (BC)^2
(AC)^2 = 9 + 16
= 25
AC = 5
So, displacement equals 5km