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unit of measure: the base unit | the supplementary unit | the derived unit

*geometry: the area of a flat figure | the area of a solid | the volume of the solid*

A ** ring** is the area bounded by two concentric circumferences on a plane.

The ** area of a ring** is the product of quarter of the value of π and the difference between the squares of the diameters of both large and small circles.

where:

d_{1} — the outer diameter;

d_{1} — the inner diameter.

*For separation of number integers and decimals, use the symbol – point [.]*

context information: contemporary and archaic unit of measurement of area