🔍 Key Concepts

• Mercator sailing relationship between difference of longitude, meridional parts, and course • How to find the difference of latitude (DLat) and difference of longitude (DLon) from a known course and distance • The sign conventions in the western hemisphere and southern latitude when applying changes to the starting position

💭 Think About

• First, from the given distance and course, think about whether the latitude at arrival should be greater or smaller in absolute value than the starting latitude. Is the track trending more north–south or more east–west? • For Mercator sailing, what trigonometric function relates the difference of longitude to the distance and the mid-latitude/meridional parts along an oblique course like 282°T? • After you compute the difference of longitude, carefully decide whether you should add or subtract it from 18°18'E to get a western longitude, and then check if the resulting longitude is in the reasonable range of the answer choices.

✅ Before You Answer

• Confirm whether the vessel is moving toward or away from the equator in latitude on a 282°T course from 34°24'S • Double-check that your difference of longitude is converted correctly from minutes to degrees and minutes before comparing to the answer choices • Verify that the final longitude is properly labeled West (W) and that its numeric value matches the approximate change you expect from your computed difference of longitude