A solid 4x4x4 cube composed of 64 smaller 1x1x1 unit cubes is painted red on all outer surfaces. How many of the 1x1x1 unit cubes have exactly two faces painted red?
24 unit cubes
Cubes with exactly two painted faces lie along the edges of the 4x4x4 cube, excluding the corners. A cube has 12 edges, and each edge contains 2 such middle unit cubes. Therefore, 12 * 2 = 24 unit cubes have two painted faces.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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