The lengths of the brass and steel rods, we need to consider their densities as well. The mass of each rod is proportional to its volume, which is proportional to the product of its length and cross-sectional area. The mass is also proportional to the density of the material. So we can write: m_brass / m_steel = (rho_brass * A_brass * L) / (rho_steel * A_steel * L) where m_brass and m_steel are the masses of the brass and steel rods, respectively, and rho_brass and rho_steel are their densities. EXPLANATION where m_brass and m_steel are the masses of the brass and steel rods, respectively, and rho_brass and rho_steel are their densities. Step 5/5 Simplifying and using the previously derived equation for the ratio of radii, we get: L_brass / L_steel = (rho_steel / rho_brass) * (r_brass / r_steel)^2 Substituting the density values for brass and steel, and the previously calculated value for the ratio of radii, we get: L_brass / L_steel = (6580 / 9584) * (0.397)^2 L_brass / L_steel = 0.091 where how did the mass of steel and brass just disappear?