the potential on the surface of a spherical conductor of radius 3m is 6v. what is the potential at its centre?

If it is spherical shell, potential is 6 v, else use the formula for spherical solid sphere in ur book

if it is spherical shell, then the answer is 6v but for solid sphere, use the formula in book the large one Q/4pie(3r2-R2)

as we knou that potential inside a apherical conduetor ia constant

hence the potential at the center will be 6v only