Here is a cereal box. Watch as it unfolds flat onto the board. 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?
Unfold a real cereal box slowly at the front as pupils settle. Take two or three hands-up answers, not open call-outs. The flat shape is its net is the phrase to plant here, but let pupils find it first.
First, a quick look at our two solids so they are fresh in mind. Each flat side of a solid is called a face. A cube has six square faces, all the same. A cuboid has six rectangular faces in three matching pairs. Point at the top, the front and one side as we name them.
Now watch a cube unfold flat and fold back again. As each square opens out, see which face it becomes: top, bottom, front, back, left and right. Six squares joined edge to edge fold up with no gaps.
Watch the cuboid unfold. Count the rectangles: there are three matching pairs. Look for the long pair (top and bottom), the tall pair (front and back) and the narrow pair (the two ends) — their sizes are different, unlike the cube's six equal squares. While we watch the screen, the real net folds the same way in my hand.
Walk each example aloud, one at a time.
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.
This round is for talking it through together — a pupil works the board while the class agrees or corrects out loud, then everyone folds at their desks.
Run it in two clear beats. Beat one (board): take a hands-up prediction — cube or not a cube? — then fold the cross on the IWB so the class watches it close with no gap. Beat two (desks): hand out one cube net and one cuboid net per group; pupils fold the real nets and lay a finger on a square to say which face it becomes. Pair a pupil who is less secure with a peer who can model careful folding. The failing arrangements come later in the Class Challenge — keep this beat on the folding case.
In your maths copy, sketch the net of a cuboid: three matching pairs of rectangles. Label which face folds to the top, which to the front and which to the side. Then mark the pairs that are the same size, so you can see at a glance that top matches bottom, front matches back, and the two ends match.
Walk the room glancing at the labels and the matched-pair marks — this is whole-class copybook practice, not marking. Watch for pupils who draw six rectangles all the same size; nudge them to check their three pairs.
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?
This round is the practice bank — a pupil works the board, the class checks each answer, and everyone confirms before moving on. Keep the board work brisk rather than over-explaining.
Run the printed six-square arrangements alongside the board: pupils fold the cut-outs to verify each prediction with their hands. The straight line and the 2×3 block are the classic non-folders — let pupils discover the gap or overlap rather than telling them. The closing question is about reasoning why a layout fails, not reaching a number. If a confident class asks how many cube nets exist, you may share that mathematicians have found eleven distinct ones, but only as a closing curiosity — the win is the reasoning, not the count, and pupils are not expected to find them all.
Why do some six-square arrangements fold into a cube while others leave a gap or two squares overlapping? What has to be true about where the squares sit for the net to close?
Listen for pupils noticing that no more than four squares can sit in one straight line, and that two squares must not land on the same face. Revoice a strong answer: so every face of the cube needs exactly one square, and the squares have to be placed so each one reaches a different face when we fold. Head off the idea that any six squares joined together will fold — the straight line and the block proved otherwise.
Next we move on to angles: what an angle is, and how we measure the amount of turn between two lines.
Keep this brisk. Hold up one folded cube and its flat net side by side as a closing image of the flat-to-3D link.
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