1. The problem statement, all variables and given/known data A cylinder of radius a with a hole through it (of radius a/2) is filled with a material of resistivity p_2. Show that the total resistivity is now 4*(pL / pi*a²) (p_2 / 3p_2 + p) 2. Relevant equations R=pL/A 3. The attempt at a solution I started with a full cylinder and a single value of p: R=pL/pi*a² Then worked my way to a cylinder with a hole in it (empty): A_full - A_hole = pi*a² - pi*(a/2)² and found A= (3/4)*pi*a² so: R = (4/3) * pL / pi*a² Now I know that I need to add both values of p somehow, but I'm unsure of the relation between 2 materials with different values of p.