A cube of side 3 units is formed using a set of smaller cubes of side ...
Total number of cubes = 9 × 3 = 27
∴Total number of faces = 27 × 6 = 162
∴Total number of non-visible faces = 162 - 54 = 108
∴ Number of visible faces / Number of non visible faces = 54/108 = 1/2
A cube of side 3 units is formed using a set of smaller cubes of side ...
Understanding the Problem
To solve this problem, we first need to visualize the setup. A cube with a side length of 3 units consists of smaller cubes, each with a side length of 1 unit.
Calculating the Number of Smaller Cubes
- The total number of smaller cubes in the larger cube is:
- Volume of larger cube = 3^3 = 27
- Therefore, there are 27 smaller cubes (1 unit each).
Faces of Smaller Cubes
- Each smaller cube has 6 faces.
- Total faces of all smaller cubes = 27 * 6 = 162 faces.
Visible Faces Calculation
- To determine the number of visible faces, we need to analyze the arrangement of the smaller cubes in the larger cube.
- The cubes on the surface of the larger cube are the ones whose faces are visible.
Identifying Visible Faces
- The cubes on the corners contribute 3 visible faces each (8 corners).
- The cubes on the edges contribute 2 visible faces each (12 edges, 1 cube per edge).
- The cubes on the faces contribute 1 visible face each (6 faces, 1 cube per face).
- By careful counting:
- Corner cubes = 8 cubes * 3 faces = 24 visible faces
- Edge cubes = 12 cubes * 2 faces = 24 visible faces
- Face cubes = 6 cubes * 1 face = 6 visible faces
- Total visible faces = 24 + 24 + 6 = 54 faces.
Calculating Non-visible Faces
- Total faces = 162 (calculated previously).
- Non-visible faces = Total faces - Visible faces = 162 - 54 = 108 faces.
Finding the Proportion
- Proportion of visible to non-visible faces = 54 : 108 = 1 : 2.
Thus, the correct answer is option 'C': 1 : 2.