Length formula: rectangular body length = (length+width+height) ×4 length+width+height = length ÷4 rectangular body length = length ×2+ height ×4 rectangular body length = right circumference ×2+ length ×4 rectangular body length = front circumference ×2+ width ×4.

Cube length = side length × 12 side length = side length ÷ 12 side length deformation;

For example, there is a gift box that needs to be tied with ribbons. The binding effect is shown in the figure. The knotted part needs 10 cm ribbon. How long does it take to do it once?

Analysis: although this question does not directly ask the length of the edge, because the ribbon binding is parallel to the edge,

Therefore, when solving a problem, we must first make sure that each color band is parallel to that side, so as to indirectly calculate the side length.

The length of the front and back ribbons = the length of the height; Left and right ribbon length = high length;

The length of the upper and lower ribbons = the length of the long ribbon. The required ribbon length = height× 4+length× 2+knotted part length 20× 4+30× 2+10 =150cm.

Knowledge point 3

Determine the shape, length, width and height of each face of a cuboid.

A cuboid has six faces, and the opposite faces are exactly the same, for example, the front and back are exactly the same, the left and right are exactly the same, and the top and bottom are exactly the same. According to the custom, we generally think that the horizontal direction is long and the vertical direction is high in a plane. According to this habit, we only need to find the required surface and determine the length and width according to the habit.