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EEJ MAIN Aptitude QUESTION #10915
Question 1
A cube is painted red on all six faces and then cut into 64 smaller equal cubes. How many small cubes have paint on exactly two faces?
  • 24✔️
  • 16
  • 8
  • 12
Correct Answer Explanation

When a cube is cut into \(4 \times 4 \times 4 = 64\) smaller cubes:

  • Cubes with 3 painted faces: Only corner cubes = 8
  • Cubes with 2 painted faces: Edge cubes (not corners). Each edge has \(4 - 2 = 2\) such cubes. A cube has 12 edges. So = \(12 \times 2 = 24\)
  • Cubes with 1 painted face: Face cubes (not on edges). Each face has \(2 \times 2 = 4\) such cubes. 6 faces = \(6 \times 4 = 24\)
  • Cubes with 0 painted faces: Inner cubes = \(2 \times 2 \times 2 = 8\)

Answer: 24 cubes have paint on exactly two faces.