There are very many equations which depend on what information you have been given.
The equation to find the volume of a rectangular object is (a) volume equals length times width times height.
If you know the density of the rectangular body you can find the volume and the plug it into this equation mass= (density)*(volume) If you have the means you can just submerge the body completely in water and find the volume of the water displaced that will be the mass as waters density is 1 g/cm^3
Volume = Length * Width * Height
the three dimensions needed to find the area of a rectangular solid object are: Height, Length and Width.
If it is a cube (basically a square) or a rectangular prism multiply the top, the length, and the base.
Volume of any prism = cross-section area times length
A rectangular prism has a volume that can be found by multiplying the object's length width and height. To obtain the mass one must also know the density of the object and multiply that by the volume.
Height x Weight x Height
length, width and height (:
Height x Weight x Height
Height x Weight x Height
Assuming the object is a rectangular parallelepiped, use its density to find its volume and solve the equation V abc for c where a, b, and c are the height, length and width respectively