Hint: A time zone is a geographical area that follows a standardised time for legal, commercial, and social purposes. Because it is more practical for locations in frequent communication to preserve the same time, time zones tend to follow the boundaries of countries and their subdivisions rather than rigidly following longitude.
Greenwich Mean Time (GMT) is the mean solar time observed at midnight at the Royal Observatory in Greenwich, London. GMT is frequently used interchangeably with UTC in English-speaking countries (UTC). GMT is identical to UT1 (the contemporary form of mean solar time at 0° longitude) when calculating, but this can deviate by up to 0.9 seconds from UTC.
The time zone used in India is known as Indian Standard Time (IST). It does not account for daylight saving time or other seasonal considerations. There is only one time zone in India. The IST is derived using the coordinates of a clock tower in Mirzapur (25.15° North Latitude, 82.58° East Longitude). IST is 5:30 hours ahead of GMT.
Since, IST is 5:30 hours ahead of GMT, then if Indian Standard Time (IST) is at 7 am, then Greenwich will be at 12:30 pm.
Note: The prime meridian is a hypothetical reference life that is used to create charts and maps. It can also be used to calculate a country's time. The north-south line at Greenwich, as the prime meridian, serves as a point of reference for all other longitude meridians that are numbered east or west of it. The reason behind the world's standard time zone system is the Greenwich meridian.