Solid cube of 6 * 6 * 6. This cube is cut into to 216 small cubes. (1 * 1 * 1).the big cube is painted in all its faces. Then how many of cubes are painted at least 2 sides ?
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56
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45
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23
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28
In a 6x6x6 cube, cubes with at least 2 sides painted are the edge cubes and corner cubes. There are 12 edges, each with (n-2) cubes, and 8 corners. Calculation: 12*(6-2) + 8 = 12*4 + 8 = 48 + 8 = 56.
To solve this question, let's consider the different types of small cubes that can be formed when the big cube is cut.
The big cube is made up of 6 x 6 x 6 = 216 small cubes.
- The corner small cubes: There are 8 corner small cubes in the big cube. Each corner small cube has 3 faces painted.
- The edge small cubes: There are 12 edges in the big cube, with each edge consisting of 6 small cubes. So, there are a total of 12 x 6 = 72 edge small cubes. Each edge small cube has 2 faces painted.
- The face small cubes: The big cube has 6 faces, each consisting of 6 x 6 = 36 small cubes. So, there are a total of 6 x 36 = 216 face small cubes. Each face small cube has 1 face painted.
Now, let's calculate the number of small cubes that are painted on at least 2 sides:
- Corner small cubes: 8 x 3 = 24 cubes (since each corner small cube has 3 faces painted).
- Edge small cubes: 72 x 2 = 144 cubes (since each edge small cube has 2 faces painted).
- Face small cubes: 216 x 1 = 216 cubes (since each face small cube has 1 face painted).
So, the total number of small cubes painted on at least 2 sides is 24 + 144 + 216 = 384.
Therefore, the correct answer is A) 56.