1, both cuboids and cubes have (6) faces, (12) edges and (8) vertices. The opposite side (exactly the same) and the opposite side (exactly the same) of a cuboid; A cube has 6 faces (exactly the same) and 12 sides (equal in length).

2. Weld a rectangular frame with iron wire, which is 8 cm long, 5 cm wide and 4 cm high. Prepare 8 cm wire (4), 5 cm wire (4) and 4 cm wire (4). At least 68 cm of wire is needed.

3. Weld a cube frame with 60 cm wire. The side length of this cubic frame is (5) cm. Because the cube has 12 identical sides, dividing 60 by 12 equals 5.

4. The top and bottom area of the cuboid is (24) cm2, the front and back areas of the cuboid are (18) cm2, and the left and right sides of the cuboid are (12) cm2.

5. The cuboids below are all composed of small cubes with a length of 1 cm. Fill in their length, width and height in brackets. In which the length is (7) cm, the width is (3) cm and the height is (3) cm, and a * * * is composed of (63) small cubes.

Knowledge of ratio

1 and the division of two numbers are also called the ratio of two numbers. Ratios can also be written in fractional form. The quotient obtained by dividing the former term by the latter term is called the ratio. The ratio can be a fraction, decimal or integer.

2. Compared with division: the former term of the ratio is equivalent to the dividend, the latter term is equivalent to the divisor, and the ratio is equivalent to the quotient; Compared with fraction, the former term of ratio is equivalent to numerator, the latter term is equivalent to denominator, and the ratio is equivalent to fractional value. The first term and the last term of a ratio are multiplied or divided by the same number at the same time (except 0), and the ratio remains unchanged, which is called the basic property of the ratio.

3, the nature of the ratio: equality: if the two terms of the ratio are equal, then this ratio is equal. For example, 2: 3 and 4: 6 are equal ratios. Multiplication property: If both terms of the ratio are multiplied by the same number, the value of the ratio remains the same. For example, 2: 3 times 2 to get 4: 6, or that ratio.