n resistances, each of r ohm, when connected in parallel give an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have a resistance in ohms, equal to

Equivalent resistance of n resistances each of r ohm in parallel is given by1R =1r +1r+....+n  times = nrso,  r = nRWhen these resistances are connected in series, effective resistance isR'=r+r+.....+ n  times = nr∴    R'=nnR=n2R