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Sorting Shapes

Shape & Space · Year 2–Year 5

Sort ten 2D shapes by two properties at once, on a Venn diagram.

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About the sorting shapes

Ten 2D shapes on a tray and two loops to drag them into. Pick what each loop is asking about, sort the shapes, and tap Check when the class thinks they are right. The shape a class is sorting is the shape itself, not its name, so the picture is on the counter and the name is what the board says.

It is the Venn diagram with shapes on it rather than numbers, which is exactly what the sorting engine was for: the machinery is about which of four places a thing belongs in, and it does not care what the thing is.

The opening question is four sides against all sides equal, and that pairing is chosen. The commonest thing a class believes about shape is that a four-sided shape with equal sides has to be a square. The rhombus sits in the middle of that Venn and is not one.

There are three properties rather than four, and the reason is the shapes rather than a shortage of ideas. Every pairing has to fill all four regions or a loop is empty and the question cannot be answered: nothing has four sides AND a curved side, and every shape with equal sides also has a line of symmetry, so both of those would leave a region with nothing in it.

The box round the loops is where shapes that fit neither go, and it matters. A class with nowhere to put a shape that fits neither loop puts it in one of them anyway.

How to use it on your whiteboard

  1. 1Pick what each loop is asking about with the buttons on the toolbar.
  2. 2Drag a shape from the tray into a loop, into the middle, or into the space outside both.
  3. 3Tap Check to mark it. Nothing is scored and nothing is timed.
  4. 4Ask which shapes could go in the middle before anyone moves one.
  5. 5Change one loop and sort the same shapes again: most of them move.

Questions

Why is a square in the middle of four sides and equal sides?
Because it is both, and so is the rhombus. That is the point of the opening question: a four-sided shape with equal sides does not have to be a square, and the rhombus in the middle is the shape that proves it.
Why are there only three properties?
Because every pairing has to fill all four regions of the diagram, and a fourth property breaks that. Nothing has four sides and a curved side, so those two loops would never overlap, and every shape with equal sides also has a line of symmetry, so that pairing leaves a region empty.
Is a square a rectangle?
Yes, and this tool does not settle that argument for you: it sorts by four sides, equal sides and right angles, and a square has all three. Whether to call it a rectangle is a conversation the properties on the board are the right way to have.
Can shapes go outside both loops?
Yes, and they have to. The box round the loops is where a shape that fits neither belongs, and it is the part a class forgets exists until there is somewhere to put one.