In an electrical cable there is a single wire of radius 9 mm of copper. Its resistance is  The cable is replaced by 6 different insulated copper wires, the radius of each wire is 3 mm. Now the total resistance of the cable will be

Initially : Resistance of given cableR=ρ lπ ×  9 ×  10−32        …..(i)Finally : Resistance of each insulated copper wire isR'=ρ lπ ×  3 ×  10−32  = 9RHence, equivalent resistance of cableReq=R'6=16×ρ lπ ×  3 ×  10−32    = 9 R6….(ii)On solving equation (i) and (ii) we get Req=7.5  Ω