Difficulty: Easy
Correct Answer: 21° 45′
Explanation:
Introduction / Context:
Converting magnetic bearings to true bearings is a frequent need when using compass observations together with maps referenced to true north. The key is handling magnetic declination with the correct sign convention: easterly declination adds, westerly declination subtracts.
Given Data / Assumptions:
Concept / Approach:
For conversion: TB = MB + declination, with east positive and west negative. Since declination is westerly, subtract its magnitude. Therefore TB = 32° − 10° 15′ = 21° 45′. True bearings are typically given as a single clockwise angle without quadrant letters.
Step-by-Step Solution:
Verification / Alternative check:
Graphically, rotate the magnetic meridian west of true north by 10° 15′; the true bearing must be smaller than the magnetic one by exactly that amount, confirming 21° 45′.
Why Other Options Are Wrong:
Common Pitfalls:
Mixing up signs; a quick rule is “East is least? No—East adds; West subtracts” when converting MB to TB.
Final Answer:
21° 45′
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