Identify the pair of # the does not belong with the other 3 there is 9/6,6/9 ; 4,1/4 ; 3/5,5 ; 2/7,7/2

The pyraminx is a rubik's cube-type toy in the shape of a tetrahedron. the pyraminx shown below has edges 15\,\text{cm}15cm long and vertical height h=12.2\,\text{cm}h=12.2cm. the triangle drawn with dashed lines is a right triangle. what is the distance rr? round your answer to the nearest tenth.