They are where three or more edges meet and form a point. Vertices are the 3D equivalent of a ‘corner’. An edge is where two faces meet it can be thought of as the equivalent of a ‘side’ of a 2D shape. Shapes like spheres, cones, and cylinders have curved faces. A face is the (in most cases) flat part of a 3D shape. Rather than ‘sides’ and ‘corners’ 3D shapes have ‘faces’, ‘edges’, and ‘vertices’. 3D shapes also have different properties to 2D shapes. We have explored how 3D shapes have height and width, just like 2D shapes, but also have depth. This can be applied to any other 2D shape. Any other six-sided shape is an irregular hexagon. For example, the traditional shape you might think of for a hexagon, with all its sides the same length, is a regular hexagon. For 2D shapes with larger numbers of sides and corners, the same rules apply. A regular triangle is an equilateral triangle, while irregular triangles include isosceles and right-angle triangles. Other 2D shapes have regular and irregular forms. Other irregular four-sided 2D shapes include rhombus, trapeziums, and parallelograms, although these shapes are not common in Key Stage 1. An irregular 2D shape has sides of different lengths and/or angles of different sizes. A regular 2D shape is a shape with all sides the same length and all interior angles the same size. Using maths terms that you might start to see in your child’s work at Key Stage 1, a square is a ‘regular’ shape, and a rectangle is an ‘irregular’ shape. While a rectangle also has four angles which are all equal and four sides, its sides are not all the same length. This is because a square is a special kind of rectangle – the length of all its sides and the size of all its angles are equal. Squares and rectangles both have four sides and four corners. Some 2D shapes have the same number of sides and corners but have different names. The only 2D shape that does not have corners is a circle – it just has one continuous side. We describe the outline of a shape between two corners as a side. The other key properties of 2D shapes are ‘sides’ and ‘corners’. We’ve already talked about how 2D shapes have height and width. For example, we could consider a triangular-based pyramid, a square-based pyramid, and a triangular prism as all different ways of drawing a ‘3D triangle’. Other 2D shapes can be made 3D in multiple ways. However, we could also describe a cylinder as a ‘circle with depth’. We could say that a sphere is a circle that has depth. Other shapes can be a bit more complicated. For example, the difference between a square and a cube is a square only has height and width, whereas a cube has height, width, and depth. This makes it ‘stick out’ into the world, rather than being flat. The difference between a 2D and 3D shape is depth – a 3D shape is a 2D shape with depth. What’s the difference between 2D and 3D shapes? This means the paper is 3D, but the drawings are 2D. You can’t pick up the drawings themselves, but you can pick up the piece of paper they’re drawn on. A piece of paper, even though it is flat, is 3D because you can pick it up. Everything in the world around us is 3D, even things that seem flat. Because 3D shapes have depth, you can pick them up and hold them. A 3D shape has 3 dimensions, height, width, and depth. What is a 3D shape?ģD stands for 3-Dimensions. To help explain this concept, you could ask your child to draw some shapes and try and pick them up off the page. Drawings are also 2D – you can draw the height and width of a shape, but you can’t pick up a drawing (just the paper it is drawn on!). The have height and width but they can’t be picked up. It is hard to find real life examples of 2D shapes, but things like shadows and reflections can be useful examples when explaining 2D shapes to children. You cannot pick up and hold a 2D shape, they are flat. A 2D shape has 2 dimensions, height, and width.
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