What are the total number of meridians at an interval of 5 degree?

Answer 1

There is no fixed set of meridians. A meridian is just an imaginary line that takes

shape when you choose any longitude and mark a little dot at every point on

Earth with that same longitude.

If you were to begin at any longitude, travel straight east or west all the way

around the Earth until you arrived back at your starting point, and make a mark

in your notebook every time you cover an interval of 5 degrees of longitude, then

you would wind up with 360/5 = 72 marks in your notebook.