Answer:
82.1 km
Explanation:
We need to resolve each displacement along two perpendicular directions: the east-west direction (let's label it with x) and the north-south direction (y). Resolving each vector:
[tex]A_x = (72) sin 30^{\circ} =36.0 km\\A_y = (72) cos 30^{\circ} = 62.4 km[/tex]
Vector B is 48 km south, so:
[tex]B_x = 0\\B_y = -48[/tex]
Finally, vector C:
[tex]C_x = -(100) cos 30^{\circ} =-86.6 km\\C_y = (100) sin 30^{\circ} = 50.0 km[/tex]
Now we add the components along each direction:
[tex]R_x = A_x + B_x + C_x = 36.0 + 0 +(-86.6)=-50.6 km\\R_y = A_y+B_y+C_y = 62.4+(-48)+50.0=64.6 km[/tex]
So, the resultant (which is the distance in a straight line between the starting point and the final point of the motion) is
[tex]R=\sqrt{R_x^2+R_y^2}=\sqrt{(-50.6)^2+(64.6)^2}=82.1 km[/tex]