MATHEWS, G. A Triangle that gives the Area and Circumference of any Circle, and the Diameter of a Circle equal in Area to any given Square. Nature 93, 110 (1914 ...
The radius of a circle or a sphere is the distance between the center and the edge. The radius can be used to calculate a circle's diameter, area and circumference. Likewise, a sphere's volume is ...
The ability to round a number to a number of decimal places or to a number of significant figures is essential if answers are to be written to the correct degree of accuracy asked for in a question.