The resistance R of a piece of wire is given by

where

is the resistivity of the material, L is the length of the wire and A is its cross-sectional area.
Using this formula, and labeling with A the aluminum and with T the tungsten wire, we can write the ratio between

(the resistance of the tungsten wire) and

(the resistance of the aluminum wire):

the two wires are identical, so L and A are the same for the two wires and simplify in the ratio, and we get:

By using the resistivity of the aluminum:

and the resistivity of the tungsten:

m we can get the resistance of the tungsten wire:
