Circumference of a circle

=

diameter X 3.1416

Area of a circle

=

square of the radius X 3.1416

Area of a circle

=

square of the diameter X 0.7854

Area of a circle

=

square of the circumference X 0.07958

Area of a circle

=

half the circumference X half the diameter

Radius of a circle

=

circumference X 0.159155

Radius of a circle

=

square root of the area X 0.56419

Diameter of a circle

=

circumference X 0.31831

Diameter of a circle

=

square root of area X 1.12838

Side of an inscribed square

=

diameter X 0.7071

Side of an inscribed square

=

circumference X 0.2251

Side of an equal square

=

diameter X 0.8862

Area of a triangle

=

base by 1/2 the altitude

Area of an ellipse

=

product of both diameters X .7854

Surface of a sphere

=

circumference X diameter

Surface of a sphere

=

square of the diameter X 3.1416

Surface of a sphere

=

square of the circumference X 0.3183

Solid contents of a sphere

=

surface X 1/16 of its diameter

Solid contents of a sphere

=

cube of diameter X 0.5236

Diameter of a sphere

=

square root of surface X 0.56419

Diameter of a sphere

=

cube root of solidity X 1.2407

Circumference of a sphere

=

cube root of solidity X 3.8978

Solid contents of a cone or pyramid

=

area of base X 1/3 altitude

Surface of a cube

=

six X area of one side

Area of trapezoid

=

altitude X 1/2 sum of parallel sides

Note - Volumes of similar solids are to each other as the cubes of their similar lines.