USEFUL DATA To find circumference of a 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 = length multiplied by breadth.  Doubling the diameter of a circle increases its area four times. To find area of a triangle, multiply base by ½ perpendicular height. Area of ellipse = product of both diameters times .7854. Area of parallelogram = 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 inscribed cube = radius of sphere times 1.1547. To find side of an equal square, multiply diameter by .8862 Squared.  A side multiplied by 1.4142 equals diameter of its circumscribing circle. A side multiplied by 4.443 equals 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 = sum of circumference of both ends times ½ slant height plus area of both ends. Contents of frustrum of cone or pyramid = multiply area of two ends and get square root.  Add the 2 areas and multiply 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. 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.