Question

Difficulty: MediumAngles of Elevation, Depression, and Bearings

A cargo ship departs from port MM and sails 24 km24\text{ km} on a bearing of 050050^\circ to reach point NN. From point NN, the ship changes course and sails 10 km10\text{ km} on a bearing of 140140^\circ to reach point PP. What is the direct distance, in kilometers, from port MM to point PP?

Answer: 26 km

Answer

The direct distance from port M to point P is 26 km.
The back bearing from N to M is 230°, and the bearing from N to P is 140°. The interior angle at N is 230° - 140° = 90°. Using the Pythagorean theorem for the right triangle formed by M, N, and P, the direct distance is √(24² + 10²) = √676 = 26 km.

Step-by-Step Solution

1
Calculate the interior angle MNP\angle MNP at point NN
MNP=(050+180)140=230140=90\angle MNP = (050^\circ + 180^\circ) - 140^\circ = 230^\circ - 140^\circ = 90^\circ
The back bearing from NN to MM is 230230^\circ. Subtracting the forward bearing to PP (140140^\circ) gives the enclosed interior angle.
2
Apply the Pythagorean theorem to right-angled triangle MNPMNP
MP=MN2+NP2=242+102=576+100=676=26 kmMP = \sqrt{MN^2 + NP^2} = \sqrt{24^2 + 10^2} = \sqrt{576 + 100} = \sqrt{676} = 26\text{ km}
Because MNP=90\angle MNP = 90^\circ, triangle MNPMNP is a right-angled triangle with hypotenuse MPMP.

Key Concept

Bearings and Right-Angled Triangles
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