# USEFUL INFORMATION

- To find area of a circle, multiply square of diameter by .7854.
- To find circumference of a circle, multiply diameter by 3.1416.
- To find diameter of a circle, multiply circumference by .31831.
- Area of a rectangle = 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 = product of both diameters x .7854.
- Area of parallelogram = base x 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 inscribed cube = radius of sphere x 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 circumferences 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 cube contents of a cone, multiply area of base by 1/3 the altitude.
- Surface of frustum of a cone or pyramid = sum of circumference of both ends x 1/2 slant height plus area of both ends.
- Contacts of frustum of cone or pyramid = multiply area of two ends and get square root. Add the 2 areas and x 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°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°F. into stream at 70 lbs. gauge pressure.
- To find capacity of tanks any size, given dimensions of a cylinder in inches, to find its capacity in U.S. gallons: 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 to it the area of all the tubes.