The class puppet is pointing at an upside-down triangle on the board and huffing: that is NOT a triangle any more — it is standing on its head!
What would you tell the puppet?
We have one test for every shape on the board: exactly three straight sides.
Watch each shape land. Before it moves, say passes or fails out loud.
Today we sort shapes into Triangle or Not a triangle.
One pupil drags at the board. Everyone else is a caller: say passes or fails before each drop. Count the straight sides first. Exactly three means it passes.
Triangle or not?
In your maths copy, draw three different triangles: one tall, one wide, one upside-down.
Now it gets trickier. Some triangles are hiding on their heads. Some fake shapes have a bendy side.
Run the three-straight-sides test every time before you drop.
Triangle or not?
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