Skip to content / Đến nội dung
ThichHocToan.com

MathNet 2017-part-07 — 172 problems (EN–VI) Question 71

Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)

Question 71

Two three-dimensional objects are said to have the same coloring if you can orient one object (by moving or turning it) so that it is indistinguishable from the other. For example, suppose we have two unit cubes sitting on a table, and the faces of one cube are all black except for the top face which is red, and the faces of the other cube are all black except for the bottom face, which is colored red. Then these two cubes have the same coloring.

In how many different ways can you color the edges of a regular tetrahedron, coloring two edges red, two edges black, and two edges green? (A regular tetrahedron has four faces that are each equilateral triangles. The figure below depicts one coloring of a tetrahedron, using thick, thin, and dashed lines to indicate three colors.)

Question illustration