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A las 14h 30m del 6 de abril de 2024, nos encontramos en situación verdadera 36º 08,0' N, 006º 13,0' W. Navegamos a 6 nudos al rumbo de aguja 116°. Calcular la situación de estima a las 16h 45m, sabiendo que el desvío de la aguja es –8° (menos) y que la declinación magnética es 5º NW.At 14h 30m on 6 April 2024 we are at true position 36º 08.0' N, 006º 13.0' W. We sail at 6 knots on compass course 116°. Calculate the dead reckoning position at 16h 45m, given that compass deviation is –8° (minus) and magnetic variation 5º NW.
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Correct answer: c) 36º 04.9' N; 005º 56.8' W
Why it is correct
Total correction = −5º − 8º = −13º, so true course = 116º − 13º = 103º. 2.25 h at 6 knots is 13.5 miles: 3.0′ south and 13.2 miles east, which is 16.3′ of longitude.
Why the others are not
- a) The working gives 36º 05,0′ N, 005º 56,7′ W, and this option does not match.
- b) The working gives 36º 05,0′ N, 005º 56,7′ W, and this option does not match.
- d) The working gives 36º 05,0′ N, 005º 56,7′ W, and this option does not match.
How to work it out in the exam
- Find the true course: true = compass + total correction.
- Distance = speed × time.
- Draw the course on the chart, measure the distance and read the position.
Where this question comes from
- Junta de Andalucía · 2024 · 1ª convocatoria · PER Modelo A · question 45 Official paper · Official answer key
- Junta de Andalucía · 2024 · 1ª convocatoria · PER Modelo B · question 44 Official paper · Official answer key
Try it: Navigation calculations
Pending instructor review. Machine translation, not reviewed.