Three solid cubes of edges 3 cm, 5 cm, 9 cm are melted together to make a new cube. 557 cm³ of this melted material is lost in the process. The surface area of the newly formed cube is -

384 cm²

Total volume of melted cubes = (3)³ + (5)³ + (9)³

                                           = 27 + 125 + 729 = 881 cm³

Since (557 cm³) is lost, remaining material weighs = 881 - 557 = 324 cm

Volume of the cube = (side)³

 ⇒ 324 = (side)³

 ⇒ side = \(\sqrt[3]{324 }\) = 8 cm

Surface area = 6 × ⇒ (side)² = 6 × 64 = 384 cm²