Solids are 3D shapes. We use solids to describe 3-dimensional objects.
It is usually interesting to know the volume and the surface area of a solid.
volume
How much space does the solid take up?
Units of volume are cubes. For example, a cube $1 \text{cm} \times 1 \text{cm} \times 1 \text{cm} = 1 cm^3$
called a cubic centimeter.
It could also be cubic meter, cubic inch, etc.
surface area
How much area does the outer (sometimes inner) surface have?
As area, surface area is measured in square units.
pyramid
cone
oblique solids
TODO
Cavalieri’s principle
sphere
review
TODO