The magnetic bearing of a line was 184°35’. If the declination at that place is 1°45’E, then the true bearing of the line would be
- A187°20’
- B186°20’Correct
- C183°50’
- D182°50’
Solution
Concept
Calculation of true bearing from magnetic bearing
Formula
True Bearing = Magnetic Bearing + Declination
Step-by-step solution
1. True Bearing equals Magnetic Bearing plus East Declination (or minus West Declination). 2. Given Magnetic Bearing = 184° 35' and Declination = 1° 45' E. Answer: B
Explanation
True bearing is calculated by adding an easterly magnetic declination to the observed magnetic bearing. Adding the declination of 1°45' East to the magnetic bearing of 184°35' yields a true bearing of 186°20'. Therefore, option B gives the correct mathematical result for the true bearing.
Why the other options are wrong
C) 183°50’ results from subtracting the declination instead of adding an eastern declination. D) 182°50’ is an incorrect subtraction of declination from the magnetic bearing.
Shortcut
True Bearing = Magnetic Bearing + East Declination (184°35' + 1°45' = 186°20').
Common mistake
Subtracting the eastern declination instead of adding it to the magnetic bearing, incorrectly yielding 182°50' (Option D).
Correct answer: B) 186°20’