To find circumference of circle -- multiply diameter by 3.1416

To find diameter of a circle -- multiply circumference by .31831

To find area of a circle -- multiply square of diameter by .7854

Area of a rectangle equals length multiplied by breadth

Doubling the diameter of a circle increases its area four times

To find area of a triangle -- multiply base by 1/2 perpendicular height

Area of ellipse equals product of both diameters times .7854

Area of a parallelogram equals base times altitude

To find side of an inscribed square, multiply diameter by 0.7071 or multiply circumference by 0.2251 or divide circumference by 4.4428

Side of an inscribed cube equals radius of sphere times 1.1547

To find side of an equal square, multiply diameter by .8862

Square. A side multiplied by 1.4142 equals diameter of its circumscribing circle

A side multiplied by 4.443 equals the circumference of its circumscribing circle

A side multiplied by 1.128 equals diameter of an equal circle

A side multiplied by 3.547 equals circumference of an equal circle

To find cubic inches in a ball, multiply cube of diameter by .5236

To find cubic contents of a cone, multiply area of base by 1/3 the altitude

Surface of frustrum of cone or pyramid equals sum of circumference of both ends times 1/2 slant height plus area of both ends

Contents of frustrum on cone or pyramid equals multiply area of two ends and get square root. Add the two areas and times 1/3 altitude

Doubling the diameter of a pipe increases its capacity four times

A gallon of water (U.S. Standard) weighs 8 1/3 lbs. and contains 231 cubic inches

A cubic foot of water contains 7 1/2 gallons, 1728 cubic inches, and weighs 62 1/2 lbs

To find the pressure in pounds per square inch of a column of water, multiply the height of the column in feet by .434

Steam rising from water at its boiling point (212 degrees F.) has a pressure equal to the atmosphere (14.7 lbs to the square inch)

A standard horse power: The evaporation of 30 lbs of water per hour from a feed water temperature of 100 degrees F. into steam at 70 lbs gauge pressure

To find capacity (in U.S. gallons) of tanks of any size, given dimensions of a cylinder in inches, square the diameter, multiply by the length and by .0034

To ascertain heating surface in tubular boilers, multiply 2/3 the circumference of boiler by length of boiler in inches and add it to the area of all the tubes