The time at Cairo is 2 hours ahead of Greenwich. Hence, it is located at

The Earth completes a full rotation of 360° in 24 hours, which translates to a rate of 15° per hour (360°/24h = 15°/h) [c3][c4]. Since the Earth rotates from west to east, places located to the east of the Prime Meridian (Greenwich) are ahead in time, while places to the west are behind [c3][c5]. Cairo is stated to be 2 hours ahead of Greenwich. To find the longitude, we multiply the time difference by the hourly rotation rate: 2 hours × 15°/hour = 30° [c2][t2]. Because Cairo is 'ahead' of Greenwich time, it must be located in the Eastern Hemisphere [c4][t2]. Therefore, a 2-hour lead corresponds exactly to 30° E longitude. This mathematical relationship is a fundamental principle of geographic coordinates and time zones [c5][t3].

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > Longitude and Time > p. 12
2. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > Longitude and Time > p. 11
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > Longitude and Time > p. 243
4. [4] Exploring Society:India and Beyond. Social Science-Class VI . NCERT(Revised ed 2025) > Chapter 1: Locating Places on the Earth > Understanding Time Zones > p. 20