How do you find volume and perimeter of spatial figures?

Answer 1

The concept of a perimeter is generally applicable for 2-dimensional figures, not solid figures.

There are several ways to find the volume and these depend on the the shape itself and the information available.

For many regular shapes there are formulae that can b used to calculate the volume. For some shapes it may be possible to consider them as being composed of smaller regular shapes and so it is simply a question of calculating their volumes and summing the results.

For some small shapes it may be possible to measure the volume by fluid displacement. Partly fill a graduated container with some liquid. Measure the amount of liquid in the container. Then very gently submerge the figure whose volume you want to find into the liquid and measure the volume again. The difference between the two volumes is the volume of the solid figure.

This method will fail if

• the solid dissolves in the liquid - for example a salt crystal in water. You may be able to find a fluid that the solid is not soluble in.
• the object is porous and you want the total space that it occupies,
• the object floats. You may be able to push it under but you have to be very careful that you take account of the volume of the obect used to push it.
• if the object is too large to move - for example, the volume of a mountain!