posted by jason .
A silver wire and a platinum wire of the same length have the same resistance. What is the ratio of the diameter of the silver wire to that of the platinum wire.
p1^L1/D1^2 = p2*L2/D2^2 since resistances are equal.
(The p's are the resistivities, which you need to look up). Since L1 = L2,
D1/D2 = sqrt(p2/p1)
subscript "1" denotes silver and subscript "2" denotes platinum.