For the cone, radius, r = 2.1cm height, h = 8.4 cm For the sphere, radius = R Cone is melted and recast into sphere. So, Volume of sphere = Volume of cone ∴ 4/3π R³ = 1/3π r² h ∴4 R³ = r² h ∴4 R³ = 2.1² * 8.4 ∴R³ = 2.1² * 8.4 / 4 ∴R³ = 2.1² * 2.1 ∴R³ = 2.1³ ∴R = 2.1 cm