If the earth’s direction of rotation is reversed, what would be the 1ST when it is noon at the International Date Line?

To understand this, first look at the current scenario. Earth rotates from West to East. The Indian Standard Time is 5 hours 30 minutes ahead of the Greenwich Meridian Time because India is to the East. The International Date Line is 180 degrees away from Greenwich, which equals a 12 hour time difference. Currently, when it is noon at the International Date Line, it is midnight at Greenwich. Since India is 5.5 hours ahead of Greenwich, the current IST would be 05.30 hrs. If the rotation is reversed, the Earth would rotate from East to West. In this case, locations to the East would be behind in time instead of ahead. Therefore, IST would become 5 hours 30 minutes behind Greenwich Meridian Time instead of ahead. When it is noon 12.00 hrs at the International Date Line, it remains midnight 00.00 hrs at the Greenwich Meridian. To find the new IST, we subtract 5 hours 30 minutes from the midnight at Greenwich. Subtracting 5.5 hours from 24.00 hrs results in 18.30 hrs. Thus, the correct option is C.