Answer:
Total of 64 cubes are needed.
Explanation:
The dimensions of smaller cube are edge length of 1 inch.
The dimensions of the formed larger cube is edge length of 4 inches.
The volume of cube is found by,
, where s is the edge length of cube.
The volume of small cubes is,
v1 =

The volume of bigger cube is,
v2 =

Let the number of cubes needed be "n".
The total volume formed is equal to n times volume of individual cube.

Thus, n = 64.