Sachin walks 20 km towards North. He turns left and walks 40 km. He again turns left and walks 20 km. Finally he moves 20 km after turning to the left. How far is he from his starting position?

Starting from the origin, track each movement: North 20 km to position (0, 20), then West 40 km to (-40, 20), then South 20 km to (-40, 0), then East 20 km to (-20, 0). The final position is 20 km directly West of the starting point. Notice that the North and South movements cancel each other out (both 20 km), leaving only the net East-West displacement.