Question

How many cubes are missing
to build a full cube?​

Answer 1

{ Refer to the attachment for the cube }

Answer:

  The number of smaller cubes missing is 20

Step-by-step explanation:

The given cube is in of 5 × 4 smaller cubes structure.

1. In the innermost place, only one horizontal gap with two column gaps, i.e., (1 × 2) = 2 smaller cubes are to be put.
2. In the middle place, two horizontal gaps are there with three column gaps, i.e., (2 × 3) = 6 smaller cubes are to be put.
3. In the outermost place, three horizontal gaps are there with four column gaps, i.e., (3 × 4) = 12 smaller cubes are to be put.

Hence the total number of smaller cubes missing is

     = 2 + 6 + 12 = 20

Answer 2

Answer:

Step-by-step explanation:

One side of the cube has only 4 cubes while the other side has 5 cubes

So in order to complete the cube a whole layer needs to be added

Hence we add 25 bricks.

And then by the given image

Cubes required to complete the outer most layer = 3×4=12

Cubes required to complete the 2nd layer = 2×3=6

Cubes required to complete the third layer = 1×2 = 2

Thus the total number of cubes required is equal to

25+12+6+2 =45

The required number of cubes is 45.

The other answer given by others is just wrong.