A Cube is coloured blue on all the faces. It is then cut into 64 smaller cubes. These cubes are now separated. The number of smaller cubes with no surface coloured is:

To make 64 cubes, we would have to cut cubes as shown below.

 N³ = 64, N=4cm ( N is the length of the side of the original cube)

Cubes painted on three sides = 8

Cubes painted on two sides = 12(n-2)= 2 × 12 = 24

Cubes painted on one side =6 (n-2)²= 4 × 6 = 24

24 + 24 + 8 = 56

Cubes that are not painted = 64 – 56 = 8

Hence, “8” is the correct answer.