1. The problem statement, all variables and given/known data rho of a hollow cylinder can be found with 4 measured quantity by the folowing formula, proof this formula 2. Relevant equations ρ= 4.m ∏.(d²-D²).h d is the outside diameter and D the inside 3. The attempt at a solution since it's my first time ever taking physics classes i'm kinda stuck (well first time taking science classes) ρ=m V so the formula of the hollow cylinder is V=∏.(d²-D²).h the 4.m should be the mass but don't realy get what the 4 is standing there for Could someone explain me how i should solve this ore give me a helping hand with the beginning of it?