If it is 1 2.00 Noon in India, on which meridian will it be 7.00 am of the same day?

Indian Standard Time (IST) is based on the 82.5° E longitude, which is 5 hours and 30 minutes ahead of Greenwich Mean Time (GMT) [2]. If it is 12:00 Noon in India, the time at GMT (0° longitude) would be 6:30 AM (12:00 minus 5.5 hours) [1]. The question asks for the meridian where it is 7:00 AM, which is 30 minutes (0.5 hours) ahead of GMT. Since the Earth rotates 15° per hour, a 30-minute difference corresponds to 7.5° of longitude (15° × 0.5) [1]. Because 7:00 AM is later than 6:30 AM (GMT), the location must be to the east of the Prime Meridian . Therefore, the meridian is 7.5° E longitude. This calculation uses the standard rate of 1° every 4 minutes or 15° per hour .

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] INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.) > Chapter 1: India — Location > INDIA – LOCATION > p. 2