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| | USAMTS Problem 1/1/14 |
 | | Taking the red 3 x 3 x 3 cube, all of the red unit-faces must be showing, and none of the “inner faces” (the faces not showing) may be red. |
 | | Also, there are exactly 8 “corner” unit cubes with 3 red faces, 12 “edge” unit cubes with 2 red faces, 6 “central” unit cubes with one red face, and 1 “inner” unit cube with no red faces. |
 | | Thus, we have exactly three unit cubes that contain only two different colors among their faces; the rest have all 3 different colors among their faces. |
| www.mit.edu /people/agustya/Math/2-15.html (1132 words) |
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