国际数学奥林匹克题 - 3 x 3 Cube
	文章来源: 于德利 于 2008-06-29 11:20:23

A 3 x 3 cube is assembled from 27 white unit cubes. The large cube is then painted black on the outside and then disassembled. If it is reassembled at random, what is the probability that the large cube is still completely black on the outside ?