Two cubes each of edge 9 cm are joined to form a single cuboid. What is the total surface area of the cuboid formed?

810 cm²

The cuboid formed by joining two cubes is:

The dimensions of the newly formed cuboid is = 18 x 9 x 9

Total surface area of a cuboid (a x b x c) = 2(ab + bc + ac) 

Total surface area of cuboid of dimensions 18 x 9 x 9 = 2[(18x9) + (9x9) + (18x9)]

                                                     = 2[162 + 81 162] = 2 x 405

                                                     = 810 cm²