The solid cube of silver, between the opposite faces of which we have to find the resistance, has a density of 10.5 g/cm^3 and a mass of 90 g.
Now density is given by mass/ volume or volume is equal to mass/ density.
Here, the volume is equal to 90/ 10.5 cm^3.
The volume of a cube with sides of length l is equal to l^3
=> l^3 = 90/ 10.5
=> l = (90/10.5) ^ (1/3) cm
=> l = 2.04 cm
=> l = .0204 m
The resistivity of silver is 15.87* 10^-9 ohm*m.
So the resistance between opposite faces of the cube is: 0.0204*15.87*10^-9
The required resistance between the opposite faces of the silver cube is 0.317*10^-9 ohm.
like justaguide said, I = 0.0204
However, the unit of the resistance he found is expressed in ohm.m^2, which is wrong. it should be ohm.
So I thing all you should do is devise the answer he found by the cross sectional area of the cube, which is I^2.
once again, i not sure of my answer because I found your question by googling it, because I wanted the answer too :D but one thing is sure: Justaguide's answer isn't logic :S