Direction: 125 cubes of similar size are arranged in the from of a bigger cube (5 cubes on each side, i. e., 5 x 5 x 5). From on corner of the top layer of this cube, four smaller cubes (2 x 2 x 1) are removed. From the column on the opposite side, two cubes (1 x 1 x 2) are removed, and from the third corner,three cubes (1 x 1 x 3) are removed and from the fourth column four cubes (1 x 1 x 4) are removed. All exposed faces of the block thus formed are coloured red.
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How many cubes have only two coloured faces?
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- 33
- 36
- 18
- 29
Correct Option: A
Only two faces are coloured is when cubes are at the edges (baring the corner cubes)
If no cubes have been removed then on each edges we will get 3 cubes that has exactly 2 faces coloured, hence total number of such cubes = 12 x 3 = 36, because we have 12 edges.
Out of these 3 cubes are removed hence required number of cubes = 36 - 3 = 33
