If local time at Cairo is two hours ahead of Greenwich Mean Time, near which longitude is Cairo located?

Introduction / Context:
Time zones around the world are based on longitude, with the Prime Meridian at Greenwich used as the reference for Greenwich Mean Time. Each hour of time difference corresponds to about fifteen degrees of longitude. This question uses that relationship to estimate the longitude of Cairo given that its local time is two hours ahead of Greenwich.

Given Data / Assumptions:

• Cairo local time is two hours ahead of Greenwich Mean Time.
• Earth rotates 360 degrees in 24 hours, so one hour of time difference corresponds to approximately 15 degrees of longitude.
• The options include 30 degrees west, 30 degrees east, 28 degrees east, 28 degrees west and 15 degrees east.
• We assume standard time zone reasoning and ignore small adjustments made by countries.

Concept / Approach:
The Earth rotates from west to east, so places east of Greenwich see the Sun earlier and have later clock times compared with Greenwich. For each hour of time difference, there is roughly a 15 degree difference in longitude. A location two hours ahead of Greenwich is therefore about 30 degrees east of the Prime Meridian. Cairo lies slightly east of 30 degrees east, but for exam purposes the correct rounded longitude is 30 degrees east.

Step-by-Step Solution:
Step 1: Use the basic relation between time and longitude. In 24 hours, Earth rotates 360 degrees, so in 1 hour it rotates 360 divided by 24, which is 15 degrees.Step 2: A difference of 2 hours corresponds to 2 multiplied by 15 degrees, which equals 30 degrees.Step 3: Cairo time is ahead of Greenwich, meaning Cairo is east of the Prime Meridian.Step 4: Combine these facts. Cairo should be around 30 degrees east longitude.Step 5: Among the options, 30 degrees east longitude matches this calculation best and is the correct answer.

Verification / Alternative check:
If you check a world map or atlas, Cairo appears slightly east of the 30 degrees east meridian, close to the Nile. Time zone maps also show Egypt in a zone that is 2 hours ahead of Greenwich. The slight difference between exact longitude and the ideal 30 degrees east rounding does not change the answer at the level of precision used in general knowledge questions.

Why Other Options Are Wrong:
Any west longitude value would place Cairo west of Greenwich, which would make its local time behind Greenwich time, not ahead. Therefore, 30 degrees west and 28 degrees west cannot be correct. The option 15 degrees east would correspond to only one hour of time difference, not two. The value 28 degrees east is close in actual geography but does not match the simple time zone calculation that leads to the rounded 30 degrees east, which is the standard exam key.

Common Pitfalls:
Some learners forget the rule of 15 degrees per hour and try to guess based on rough map memory, which can lead them to pick a near value like 28 degrees east without understanding the method. Others confuse ahead and behind and accidentally choose a west longitude. To avoid mistakes, remember that going east adds hours, going west subtracts hours, and use the 15 degrees per hour guideline to make a quick and accurate estimate.

Final Answer:
If Cairo is two hours ahead of Greenwich Mean Time, it is located near 30 degrees east longitude.