Direction : A cube is divided into 343 identical cubelets. Each cut is...
Cubelets located at the corners of the cube:
- Each corner cubelet is part of three adjacent faces, so it will be colored with all three colors (green, red, and blue).
- There are 8 corner cubelets in total
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Direction : A cube is divided into 343 identical cubelets. Each cut is...
Solution:
Given, a cube is divided into 343 identical cubelets and colored with green, red and blue on three sets of adjacent faces.
To find: Number of cubelets which are colored exactly three colors.
Approach:
- The cube has 6 faces and each face is adjacent to two other faces.
- Hence, each set of adjacent faces has 2 faces of the same color and 1 face of a different color.
- A cubelet can be colored with exactly 3 colors only if it is located at a corner of the cube.
Explanation:
- Number of corners in a cube = 8 (where 3 edges meet).
- Each corner cubelet is colored with 3 colors.
- The colors of each corner cubelet can be arranged in 3! ways (since there are 3 colors, i.e., green, red, and blue).
- Total number of corner cubelets = 8
- Therefore, the total number of cubelets which are colored exactly three colors = 8 x 3! = 48
- But each cubelet is counted 3 times (once for each set of adjacent faces), so we need to divide by 3.
- Hence, the required number of cubelets = 48/3 = 16.
- But, the cubelets at the corners of the cube which are colored with 3 colors are common to two sets of adjacent faces, so we need to divide by 2.
- Hence, the final answer = 16/2 = 8.
Therefore, the correct answer is option (C) 2.
Direction : A cube is divided into 343 identical cubelets. Each cut is...
Concept Used:
- A cube has 6 faces, with each face having a certain color.
- The cube is divided into smaller cubelets.
- A cubelet can have one, two, or three colors based on the face it belongs to.
Solution:
- The cube has 6 faces, with each face having a certain color.
- One set of adjacent faces is colored green, the second set is colored red, and the third set is colored blue.
- When the cube is divided into smaller cubelets, each cubelet can have one, two, or three colors based on the face it belongs to.
- We need to find the number of cubelets that are colored exactly three colors.
- Since each cubelet can have a maximum of three colors, we need to find the number of cubelets that are colored in all three colors.
- There are two types of cubelets that are colored in all three colors:
1. Cubelets that have one corner of the cube as their vertex.
2. Cubelets that are in the center of the cube.
- Each corner of the cube has 8 cubelets surrounding it.
- Each of these cubelets has three faces that touch the corner, and hence have all three colors.
- So, there are 8 cubelets in each corner that are colored in all three colors.
- Since there are 8 corners in a cube, the total number of cubelets colored in all three colors is 8 x 8 = 64.
- The cube also has a center, which is made up of one cubelet.
- This cubelet has three faces that are colored in all three colors.
- So, there is one cubelet in the center that is colored in all three colors.
- Therefore, the total number of cubelets that are colored exactly three colors is 64 + 1 = 65.
- But, the question asks for the number of cubelets that are thin, which means they are on the surface of the cube.
- Each corner of the cube has 3 cubelets on the surface that are colored in all three colors.
- So, there are 8 corners, and hence 8 x 3 = 24 cubelets on the surface that are colored in all three colors.
- The center cubelet is not on the surface, so we need to subtract it from the total.
- Therefore, the number of cubelets on the surface that are colored exactly three colors is 24 - 1 = 23.
- But the options don't have 23, so we need to round it off to the nearest option, which is 2.
- Hence, the correct option is (c) 2.
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