Here is a cereal box. Watch as it unfolds flat at the front. What shape did the box become once it lay flat? And do you think we could fold it back to look exactly like a box again?

Watch the solids unfold flat into their nets and fold back up again. A flat side of a solid is called a face. As each one folds, keep your eye on where each face ends up.

First, all eyes on the board. Here are six squares in a cross. Predict together: will they fold up into a cube? We will fold to check and watch each square close into place with no gap. Once we have folded it together on the board, turn to the real net on your desk: fold your own cube net and cuboid net, and lay a finger on a square to name the face it becomes — top, front and side.

Today we work through these arrangements together. For each one, predict folds into a cube or does not fold before we fold to check. Some leave a gap where a face is missing; some have two squares that would land on the same face and overlap. The screen reveals the gap or the overlap when an arrangement fails. We finish with a thinking question, not a counting one: there are many ways to lay out six squares, and only some make a cube net — can you explain what has to be true for a layout to fold up?

Today's big ideas

• A net is the flat shape that folds up into a solid, with every face laid out side by side.
• A cube net is six squares that fold with no gaps and no overlaps; not every arrangement of six squares works.
• A cuboid net is three matching pairs of rectangles: top and bottom, front and back, the two ends.