Students form right rectangular prisms from clay and make parallel and perpendicular plane cuts (Activity 1), then observe and record that parallel cross sections are congruent to the base and perpendicular cross sections are rectangles congruent to opposite faces. Students form rectangular pyramids and make horizontal (parallel) and vertical (perpendicular) slices (Activity 2), then observe and record that parallel cross sections are similar to the base (different sizes) and perpendicular cross sections can be triangles or trapezoids. The activity pages require students to name or sketch the 2D shapes produced by slices of rectangular prisms, hexagonal prisms, cubes, and rectangular pyramids, and the answer keys explicitly identify the resulting polygons.

Activity 3 presents cross sections of a rectangular prism (Archie's box) and has students identify that dividers taken perpendicular to the base are rectangles with the same dimensions as the side faces (12 in. by 5 in.) and compute their area. The lesson also gives a triangular-prism example in which students find a triangular cross section congruent to the prism base and compute its area, and a square-pyramid example in which students find a cross section parallel to the base, determine its side lengths via a 1/4 scale factor, and compute its area using the scale factor squared. The Student Activity pages require students to find lengths, widths, and areas of cross sections for rectangular and triangular prisms and for a square pyramid, with worked answers showing congruence and similarity reasoning.

Students are asked multiple times to identify or name the 2D shape produced by a slice (e.g., Section 3 asks for shapes from parallel slice A and perpendicular slice B; Section IV and other problems ask for the cross-section of triangular pyramids and rectangular prisms). The practice and test pages include items where students choose which slice produces a triangle or rectangle, decide whether parallel or perpendicular slices yield uniform (congruent) cross sections for a hexagonal prism, and compute areas of slices parallel to bases (candy bar, butter problems). The Parent Plan Skills explicitly restates the standard: "Describe the two-dimensional figures that result from slicing three-dimensional figures, as in plane sections of right rectangular prisms and right rectangular pyramids."