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Q3 (IAS/1999) Geography › Maps & Locations › Geographical lines and coordinates Answer Verified

If it is 10.00 a.m. IST., then what would be the local time at Shillong on 92°E longitude ?

Result
Your answer: —  ·  Correct: B
Explanation

Indian Standard Time is the time at the 82.5°E standard meridian (IST = time at 82°30′E) [1]. The Earth rotates 360° in 24 hours, so each degree of longitude corresponds to 4 minutes of time; moving eastward advances local time [2]. Shillong at 92°E is 92.0° − 82.5° = 9.5° east of the standard meridian. The time difference is 9.5° × 4 minutes/° = 38 minutes. Therefore, when IST is 10:00 a.m., local solar time at Shillong is 10:00 + 0:38 = 10:38 a.m. Hence the correct option is 2 (10.38 a.m.).

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > Indian Standard Time > p. 245
  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
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