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A die is a solid — a shape with depth. Open a cardboard box out flat. The flat shape is a net. Fold the net back up and the box is whole again.

This is Part II, Chapter 4, Exploring Some Geometric Themes.

What you will learn

• Faces, edges, corners — count the parts of a solid.
• A net that folds up — six joined squares fold into a cube.
• Nets that fail — most ways of joining six squares do not close.
• Views — the flat shape you see from the front and from above.
• Prisms and pyramids — the counts for any number of sides.
• Fractals — a rule used again and again on its own result. Three examples are the triangle, the snowflake and the carpet.

Each lesson has a lab, apart from the summary and quiz. Tap it or slide it, and watch.