A tetrahedral puzzle is made of smaller tetrahedrons. One face of the larger tetrahedron is shown divided into smaller ones. Assuming all faces are the same, how many small tetrahedrons are there on the faces of the larger tetrahedron?
X1 is a 3D form generated from the shape X, using certain 3D operations. It has 11 surfaces in total. If the same operations are carried out on shape Y, how many surfaces would the resulting 3D form have?
Shown below are sole designs of slippers, of which some are matched-pairs (one left foot and one right foot). Identify the total number of matched-pairs in the image.
