3D shapes and nets

Hello, and welcome to Myriora Maths! A dice, a tin of beans, a pyramid. These are solid shapes. Let's count their faces, edges and vertices, and see how to make them from flat paper.

Look at this cube. The flat surfaces are called faces: a cube has six. The lines where two faces meet are edges: a cube has twelve. And the corners are vertices: a cube has eight.

A cuboid is like a stretched cube, with six faces, twelve edges and eight vertices too. A square-based pyramid has five faces, eight edges and five vertices. A cylinder has two flat circle faces and one curved surface.

If you unfold a box flat, you get its net. This is a net of a cube: six squares in a cross shape. Fold up the sides, and it makes a cube again.

Let's try one together. How many faces does a cuboid have? Say it out loud!

A cuboid has six faces, just like a cube!

Here's a question that catches lots of people. How many edges does a cube have? Some people count four edges on each of the six faces, and say twenty-four. But every edge is shared by two faces, so each one got counted twice. Twenty-four halved is twelve edges!

Your turn! How many faces does a triangular prism have? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! It has two triangle faces at the ends, and three rectangle faces round the side. That's five faces!

Quick review. Faces are the flat surfaces, edges are where two faces meet, and vertices are the corners. A cube has six faces, twelve edges and eight vertices. A net is a solid shape unfolded flat. See you next time!