🔍 Key Concepts

• Parallel sailing: distance on a parallel of latitude depends on the difference in longitude and the cosine of the latitude • Conversion of difference of longitude (DLo) from degrees and minutes to decimal degrees and then to nautical miles along a parallel • Use of the Earth’s circumference at the equator (60 NM per degree of longitude) adjusted by cosine of latitude

💭 Think About

• First, compute the numerical difference of longitude between 13°54'E and 42°48'W, being careful with E/W signs • Then, convert that longitude difference into an equivalent distance along the equator, and finally multiply by the cosine of 23°24' to get distance along the parallel • Compare your calculated distance to the answer choices, paying close attention to rounding and significant figures

✅ Before You Answer

• Confirm your DLo in degrees is E+W added together, not subtracted, because the longitudes are on opposite sides of the prime meridian • Make sure you use cos(latitude), not sin, and that your calculator is in degrees, not radians • After computing the raw distance, check if a one- or two-decimal rounding could shift you to the nearest multiple-choice option