Duration: 1- 2 hours
To introduce the unit, show a three-dimensional objects, such as a cereal box or cup. Ask what shape makes up the object if it were cut and flattened. Demonstrate how a cup is made up of a circle and a rectangle; and a cereal box is made up of rectangles and squares. You can show other examples, or give small groups objects to figure out the shapes that make up the object.
Explain that a "net" is a two-dimensional shape that, when folded, encloses a three-dimensional object. Show (or distribute) a net for a cube, explaining that each side of the cube is called a "face", and then put the cube together. Discuss how you can draw a net for an object by visualizing what it would look like if you cut along the edges and flatten it out.
Check for student understanding of identifying shapes in 3-D objects, and trying to create a net for the shape. The pre-test shows a collection of 3-D objects and asks students to count the faces for a select few, as well as draw the 2-D shapes of each face. Consider presenting the 3-D objects to the entire class on a whiteboard or poster.Review the pre-test, by having students share and explain the shapes used in the 3-dimensional objects. Discuss the techniques students used to determine the faces that make up each shape? Where did they make mistakes, and what might have caused them?