🔍 Key Concepts

• Time zones and zone descriptions: Each zone description usually covers 15 degrees of longitude, corresponding to one hour of time difference from Greenwich Mean Time (GMT/UTC). • Relationship between zone numbers and longitude: Zone description numbers increase going eastward from the Prime Meridian and decrease going westward. • Mid-meridian concept: Each standard time zone has a central (mid) meridian; the boundaries between adjacent time zones are typically halfway between their mid-meridians.

💭 Think About

• First, recall what longitude range is normally covered by any single 1‑hour time zone and how many degrees that is. • Think about where the mid‑meridian for zone description +7 would lie, and where the mid‑meridian for +8 would lie; then determine the longitude exactly halfway between them. • Translate the zone description number (e.g., +7, +8) into its corresponding standard mid‑meridian longitudes using the usual formula used in navigation texts.

✅ Before You Answer

• Confirm how many degrees of longitude per hour of time difference from UTC are assumed in standard nautical time‑zone problems. • Verify the formula that relates zone description (ZD) to the standard time meridian in degrees of longitude, including the correct sign convention for + (east) and − (west). • Calculate the mid‑meridians for ZD +7 and ZD +8 and then find the longitude halfway between them, and compare that result carefully to each answer choice.