Two towns X and Y are situated on the Equator. If town X is on the Greenwich Meridienand town Y is on…

Analyze the question: Town X is at 0° (Greenwich Meridian) and Town Y is at 45°E. When X's time is 4:00pm, we need Y's time.

Concept: The Earth rotates 360° in 24 hours, so:

• 360° ÷ 24 hours = 15° per hour, which is 4 minutes per 1° of longitude.
• Places east of a reference meridian are ahead in time (the sun rises there first), so we add.
• Places west are behind, so we subtract.

Solution:

1. Longitude difference = 45° − 0° = 45°
2. Time difference = 45° ÷ 15° per hour = 3 hours
3. Y is east of X, so Y is ahead: 4:00pm + 3 hours = 7:00pm

Tip: Remember "East is Early (ahead), West is Wait (behind)", or "ERA": East Rises Ahead. Always divide the longitude difference by 15 to get the hours, and then add for east or subtract for west. If the two places are on opposite sides of Greenwich, add their longitudes before dividing.