On 21 May at 0630 PDT, (ZD +7), your vessel takes departure at the San Francisco Sea Buoy, LAT 37°45.0'N, LONG 122°41.5'W, enroute to Kobe, LAT 33°52.0'N, LONG 135°00.0'E via great circle. The distance is 4,245 miles, and you estimate that you will average 14.0 knots. What will be your estimated zone time of arrival?
• Use the basic time–speed–distance formula: Time = Distance ÷ Speed and convert the answer into days, hours, and minutes. • Understand how to convert between zone time (ZT) and Greenwich Mean Time (GMT/UT) using the zone description (ZD). • Determine the correct zone description for Kobe’s longitude (135°E) and carefully track each time-zone conversion step.
• First, compute how many hours (and minutes) it will take to travel 4,245 miles at 14 knots. Is that closer to 12 days, 13 days, or 14 days? • After you get the travel time in days and hours, add it to your departure ZT (PDT, ZD +7) by first converting departure ZT to GMT, then adding the travel time. • Once you have your GMT at arrival, convert that to Kobe local zone time using the correct ZD for 135°E, and then match both the date and time to one of the answer choices.
• Double-check your Time = Distance ÷ Speed calculation, including conversion of decimal hours to minutes. • Confirm your sign convention: west longitudes generally have positive ZD, east longitudes generally have negative ZD. • Verify that when you cross the International Date Line, the date (not just the clock time) changes appropriately before choosing your final option.
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