The ACT sometimes likes to include questions that involve 3D objects that have a number of faces on the object. The faces on the object will be common geometric shapes such as triangles, squares, or occasionally more complex shapes such as hexagons.

Key things to remember for faces on 3D figure questions are:

• Shared Edges: Faces on the shape will have shared edges. Each edge will be shared by two faces, and each face will have the same numbers of edges as it has sides.
• Area: the area of the shape is equal to the summed area of all of the individual faces

Here is a sample question from the April 2017 ACT:

There are 20 sides to the die, each of which has 3 edges. Each edge is shared by two faces. Therefore the number of sides = 

(20∙3)2=30. The answer is D.