How many of the cubes have at most faces painted? 205 144 210 None of these Let

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Question
How many of the cubes have at most faces painted?
Options
A. 205
B. 144
C. 210
D. None of these

Correct Answer

205

Explanation

Let us see the changes due to removal of cube from corner-
Number of vertices with three faces exposed (Painted) is 7 + 3 = 10
Number of Cubes with 2 sides exposed (Painted): In general one edge gives us 4 (n - 2 in general case) cubes with two face painted but in this case out of 12 edges only 9 edges will give us 4 cubes in one edge and remaining 3 edges will give us 3 cubes from one edge, hence total number of edge is 9 x 4 + 3 x 3 = 45
Number of Cubes with 1 side exposed (Painted): It will remain same as normal case i.e. 6(4²) = 96
Number of Cubes with no sides exposed (Painted) is 4³ = 64
From the above observation:
From the above explanation number of the cubes with at most 2 faces painted is 64 + 96 + 45 = 205.
Or else 215 - 10 = 205