Find the difference vertically( North and South) and the difference horizontally ( East and West)
Then use the Pythagorean Theorem.
600 North - 200 South = 400 m
400 West - 100 East = 300 m
Now using the Pythagorean Theorem;
400^2 + 300^2 = total displacement^2
Total displacement^2 = 160,000 + 90,000
Total displacement^2 = 250,000
Total displacement = √250,000
Total displacement = 500 m