The relationship between the resistance R of a wire and its resistivity 
is given by
where L is the length of the wire and A is its cross sectional area.
In the problem, we have
, 
and 
. So we can solve the find the area A:
For a cylindrical wire, the cross sectional area is given by
where r is the radius. We know the value of the area A, so now we can find the radius of the wire:
where L is the length of the wire and A is its cross sectional area.
In the problem, we have
For a cylindrical wire, the cross sectional area is given by
where r is the radius. We know the value of the area A, so now we can find the radius of the wire: