Sometimes Internet inquiries just strike: how to find the weight or volume of a triangle, square or circle. The answer – in any way. A square, a triangle, etc. – flat figures, calculation of weight and volume it is possible only at volume figures. And the cube or a parallelepiped can be meant by a square, one of the parties of which represents a square. Knowing parameters of these figures, it is possible to find both the volume and weight.

## Instruction

1. For calculation of volume of a cube or a parallelepiped you have to know three sizes: length, width and height. The volume and density of material of which the subject is made are necessary for calculation of weight (m = v*ρ). Density of gases, liquids, breeds, etc. can be found in the corresponding tables.

2. Example 1. Find **the mass** of the granite block which length of 7 m, width and height on 3 m. The volume of such parallelepiped will be equal to V = to l*d*h, V = 7m*3m*3m = 63 m³. Density of granite is 2.6 t/m³. Mass of the granite block: 2.6 t/m³ * 63 m³ = 163.8 t. Answer: 163.8 tons.

3. It is necessary to consider that the studied sample can be non-uniform or contain impurity. In that case you will need not only density of the main substance, but also density of impurity.

4. Example 2. Find the mass of a cube with the party of 6 cm which for 70% consists of a pine, and for 30% from a fir-tree. Cube volume with the party of l = 6 cm is equal to 216 cm³ (V=l*l*l). The volume which is occupied in a sample by a pine can be calculated through a proportion: 216 cm³ - 100%X – 70%; X = 151.2 cm³

5. The volume which occupies a fir-tree: 216 cm³ - 151.2 cm³ = 64.8 cm³. Density of a pine of 0.52 g/cm³, so mass of the pine which is contained in a sample of 0.52 g/cm³*151.2 cm³ = 78.624 g. Density of a fir-tree of 0.45 g/cm³, respectively - weight is equal to 0.45 g/cm³*64.8 to cm³ = 29.16 g. Answer: lump of the sample consisting of a fir-tree and a pine of 78.624 + 29.16 = 107.784 g

6. And even if you need to calculate the mass of a square metal leaf, then you will calculate the mass of a parallelepiped, l which length, width of d and height (leaf thickness) of h.

7. Example 3. Find the mass of square brass plate of 10 cm by 10 cm which thickness of 0.02 cm. Density of copper is 89.6 g/cm³. Volume of brass plate: 10 sm*10 sm*0.02 cm = 2 cm³. m (sheet) = 2 cm³*89.6 of g/cm³ = 179.2 g. Answer: the mass of a leaf - 179.2 g.