Shape to name
Draw a random 2D or 3D shape with the property that defines it.
Runs locally in your browser. Nothing you generate is ever sent to a server.
Press "Generate Shape" to see a result here.
Group
Press Generate and a shape comes up with the property that defines it - how many sides, how many faces, which angles. The list covers flat shapes, solid shapes and the classification of triangles.
A square is a rectangle. A rectangle is defined as a quadrilateral with four right angles, and a square has those plus four equal sides - so it belongs to the category, in the same way that a poodle is a dog. The reason this feels wrong is that in everyday speech "rectangle" implies "not a square", but definitions in geometry are inclusive rather than exclusive. It is one of the most useful arguments to have in a maths lesson.
By sides they are equilateral, isosceles or scalene. By angles they are right-angled, acute or obtuse. Both classifications apply to every triangle simultaneously, so a triangle can be isosceles and right-angled at the same time. Pupils often assume they are picking from one list of six.
Working through shapes in the order a book presents them lets pupils anticipate what comes next, and anticipation does most of the work that recall was supposed to do. Drawing at random removes that crutch, which is why it is harder and why it tests what has actually stuck.
For solid shapes the three counts that matter are faces, edges and vertices. A cube has 6, 12 and 8. A tetrahedron has 4, 6 and 4. There is a pattern underneath: for any simple solid, faces plus vertices minus edges always equals two. It holds for the cube (6 + 8 - 12), for the tetrahedron (4 + 4 - 6), and for every other solid in this list, which makes it a good thing to have a class check rather than be told.
A rhombus is a parallelogram. A square is a rhombus and a rectangle and a parallelogram all at once. These overlaps confuse pupils because everyday language treats the words as mutually exclusive, while geometry treats them as nested categories. Drawing shapes at random and asking what else each one is turns that confusion into the actual lesson.
Draw five shapes and find each one in the room. Hexagons turn up in tiles and bolt heads, cylinders in cups and pipes, trapeziums in lampshades. The exercise works because it moves shapes from the page to the world, and children remember the bolt head long after they have forgotten the diagram.
The list is filtered to the group you chose, then a shape is drawn using your browser's cryptographic random source with rejection sampling, so nothing is favoured. Batches without repeats use a Fisher-Yates shuffle driven by the same source.
Press Generate and one comes up with a short description of what defines it.
Yes. The filter separates flat shapes, solid shapes and the types of triangle.
Yes. A rectangle is any four-sided shape with four right angles, and a square meets that plus having all sides equal. Every square is a rectangle; not every rectangle is a square.
Yes. Drawing shapes at random is better practice than working through a textbook order, because pupils cannot anticipate what is coming next.
Yes. Set the quantity and press once, then Copy All to take the list with descriptions.
Yes. Each shape is drawn with your browser's cryptographic random source, so everything in the chosen group has an equal chance.
Six faces, twelve edges and eight vertices. Faces plus vertices minus edges equals two, which holds for every simple solid shape.
Yes. A parallelogram has two pairs of parallel sides, and a rhombus has that plus four equal sides. Squares belong to both categories as well.