Calculate the location of a place where the local time is noon when it is 7:30 p.m. at Greenwich.
Time at Greenwich = 7:30 pm
Greenwich is the 0°longitude.
Time at given place = 12 pm
Difference between the time at both places = 7 hours 30 mins.
Since the time at given place is less than that at the Greenwich meridian, the place is to the west of it.
It takes 4 minutes for the earth to cover 1°
Therefore, it will take 60 minutes (1 hour) to cover 15°
So, the Earth will cover 112.5°(15 x 7.5) in 7.5 hrs
Thus, the location of the place is 112.5°West