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imc

counting and probability intermediate

Problem

Each of the edges of a cube is labeled or . Two labelings are considered different even if one can be obtained from the other by a sequence of one or more rotations and/or reflections. For how many such labelings is the sum of the labels on the edges of each of the faces of the cube equal to ?
(A)
(B)
(C)
(D)
(E)
Solution
For simplicity, we will name this cube by vertices, as shown below. Note that for each face of this cube, two edges are labeled and two edges are labeled For all twelve edges of this cube, we conclude that six edges are labeled and six edges are labeled We apply casework to face Recall that there are ways to label its edges: 1. Opposite edges have the same label. There are ways to label the edges of We will consider one of the ways, then multiply the count by Without loss of generality, we assume that are labeled respectively: We apply casework to the label of as shown below. We have such labelings for this case. 4. Opposite edges have different labels. There are ways to label the edges of We will consider one of the ways, then multiply the count by Without loss of generality, we assume that are labeled respectively: We apply casework to the labels of and as shown below. We have such labelings for this case. Therefore, we have such labelings in total.
Final answer
E