We are given two displacement vectors. One in north direction other in east direction. We know that north and east directions are perpendicular to each other. Hence, the displacements vectors are also perpendicular to each other. Therefore, there resultant can be found by using Pythagora's Theorem like rectangular components method.
D = √(Dₓ² + Dy²)
where,
D = Magnitude of vector sum of both displacements = ?
Dₓ = Magnitude of Displacement Vector in east direction = 30 m
Dy = Magnitude of Displacement Vector in North Direction = 100 m
So you problem ask to find or calculate the approximate diameter of the planet Neptune, based on my calculation the diameter of Planet Neptune would be 5972. I hope you are satisfied with my answer and feel free to ask form more.