Sorting solids

In your book, Maths Mela (Chapter 1), you sort solid shapes in different ways. One way is by the number of flat faces. A cone has 1 flat face, a circle at its bottom. A cylinder has 2 flat faces, a circle at each end. A triangular pyramid has 4 flat faces. A square pyramid has 5, and so does a triangular prism. A cube and a cuboid have 6. A hexagonal prism has 8: its 2 hexagon ends and 6 rectangles.

Another way is curved or flat. A sphere, a cone and a cylinder have a curved face, one you could roll. Cubes, cuboids, prisms and pyramids have only flat faces.

The book also sorts solids with two circles that overlap. One circle is for solids with rectangular faces. The other is for solids with triangular faces. The part where the circles overlap is for solids that have BOTH. A triangular prism has triangles and rectangles, so it goes in the overlap. A rectangular pyramid (a pyramid on a rectangle base) has a rectangle and triangles, so it goes in the overlap too.

A cuboid has only rectangles, so it goes in the rectangle circle alone. A triangular pyramid has only triangles, so it goes in the triangle circle alone. A sphere, a cone and a cylinder have no rectangles or triangles at all, so they go outside both circles.