A ship sails 3 nautical miles due south, then 12 nautical miles due west, and then another 12 nautical miles due north. How far, in nautical miles, is the ship from its starting point ?

After sailing 3 south and 12 north, the ship is 9 nautical miles north of its starting latitude. The 12 nautical mile west movement is perpendicular. Using Pythagorean theorem: distance = √(9² + 12²) = √(81 + 144) = √225 = 15 nautical miles. This forms a 9-12-15 Pythagorean triple, a multiple of the classic 3-4-5 triangle.