If rounding the initial division of longitude by 15 yields ambiguity, which method should be used to determine the offset?

• A. Round the division result to the nearest whole number.
• B. Divide minutes by 60, add to degree, and divide by 15.
• C. Increase the degree by 1 if minutes exceed 30.
• D. Consult a time zone map.

Answer: (B)

When you need the exact offset from UTC from longitude, you must convert the longitude into a precise offset before turning it into hours. Convert minutes to a fraction of a degree (minutes/60), add that to the degrees to get total decimal degrees, then divide by 15 to express that total as hours. This directly gives you the offset in hours (and minutes, if you work it out), with the correct sign for east or west. Rounding the initial division can push you into the wrong time zone near a boundary, and rough rules like “increase the degree if minutes exceed 30” aren’t reliable. A time zone map is only a general guide and doesn’t provide the precise offset needed for navigation, since political borders and daylight-saving rules vary.