A large cube is formed by using many small 1"x1"x1" cubes. Once the large cube is formed, all the outside faces are painted. There are now exactly 27 small cubes that do NOT have any paint on any face. How many 1"x1"x1" cubes were used to form the large cube?

Answer 1

3^3 = 27 = # of cubes not painted. There needs to be one cube outside of every one of these cubes on each side of all the non-painted cubes= 5^3 = ?

Answer 2

125