Then appropriate to compare this figure with a well-known children close in the form of the figure of the same volume, for example, a quadrangular prism of the general form of a cube. At this stage can be shown to children with conventional measurements, that all sides (ribs) in the cube are of equal length, while the general form of the prism adjacent (coming from a single vertex) edges have different lengths. The next stage is compared more closer to form shapes such as rectangular and triangular prisms. For this we need to compare the shape of the base shape (rectangle – a triangle), number of corners (eight – six). One can show that rectangular prisms can always build a tower, and from the triangular – only when they are on the ground, and if a triangular prism lies on its side, it can be used as a roof for the house. In children 5-6 years longer capable of distinguishing similar in form plane and solid figures.

Therefore, at this stage is proposed to compare the figures of similar shape with different dimension. Thus, the cube is compared to the square. For this proposed hide between the lines with his hands (or hand and the table surface), first flat, then a volume figure. It turns out that a plane figure is hiding in her hands, and the volume – not hidden. For this purpose we can offer group figures in the game "Mail": flat figures – "envelopes" – held in a mailbox slot, and three-dimensional figures – "send" – do not pass.

Another method of comparing the planar and three-dimensional figures is to count the corners. So, quadrangular prism has 8 corners, while the quad – 4. In addition, it is important to pay attention to children that are flat and three-dimensional figures are used in different kinds of structural and representational activities. And in application process and drawing bulky items described with the corresponding plane figures. For example, the roof of the house, having the shape of a triangular prism, the figure is depicted as a triangle. In children 5-7 years able to perceive geometric figures as benchmarks, using which people define the shape of objects. At this stage they are able to sign forms to abstract from the objects themselves. This helps them understand the relationship between characteristic properties of a figure and its title. In order to teach subjects to generalize on the form, you must give the children a few models of the same geometric shapes of different colors, sizes, with different proportions of parts arranged differently in space. Kids are invited to examine these figures and find the differences, similarities and, finally, to call this group of figures in one word. Then the children are given the following exercise: to say that the total of all items proposed (children must understand that, regardless of the various features, objects have the same form) to find items that have called the form. In this type of exercise teacher should ensure that children did not use the names of plane figures to denote a form of volumetric objects. Two variants are allowed to refer to speech forms three-dimensional figures: using the names of three-dimensional figures (Eg "cabinet has the shape of a prism") with double names of the form (for example, "cabinet volume has a rectangular shape"). In this example, we can not say: "The cabinet has a rectangular shape" as a case – it volumetric object, and a rectangle – a flat intellectual training of the child to school