To find the diameter of a circle: Multiply the circle by .31831.
To find the area of a circle: Multiply the square of the diameter by .7854.
To find the area of a triangle: Multiply the base by one-half the perpendicular height.
To find the surface of a ball: Multiply the square of the diameter by 3.1416.
To find the solidity of a sphere: Multiply the cube of the diameter by .5236.
To find the cubic contents of a cone: Multiply the area of the base by one-third the altitude.
Doubling the diameter of a pipe increases its capacity four times.
To find the pressure in pounds per square inch of a column of water: Multiply the height of the column in feet by .434.
Standard Horse-power: The evaporation of 30 pounds of water per hour from a feed water temperature of 1,000 degrees Fahrenheit into steam at 70 pounds gauge pressure