Mr. X walks 1 km towards east and turns right and walks 3 km. He again turns left and walks 4 km. Finally, he walks 15 km north. How far is he from the starting point?

Explanation

Take the starting point as (0, 0). After 1 km east, he is at (1, 0). Turning right means south, giving (1, −3). Turning left from south means east, so after 4 km he is at (5, −3). Finally, 15 km north gives (5, 12). Hence d = √(5² + 12²) = 13 km.