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 formula for finding the area of a circle is 𝑨 = π𝒓² 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 ...

Most wire or string is made with a circular cross section of some particular radius and diameter. The area of that cross section is the well known A = pi*R² which is colloquially pronounced as “pie ...