Question 3
What happens to the total surface area if that 2 cm cube is cut into 8 small cubes 1 cm along each edge?
The right answer is the one marked above.
It doubles, to 48 cm2. The 6 faces of one small cube come to 1 cm2 × 6 = 6 cm2, and there are 8 of them: 6 cm2 × 8 = 48 cm2.
The number of cubes goes up eightfold but the area does not — only the faces that were hidden inside the original cube are newly exposed. The mass does not change at all.