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40 and adding a ¼-inch double edge all around. The double seam on this pail is of the same construction as the one shown in Fig. 36. The wire edge is added to the top of the stretchout. Using the bail shown in the elevation as a profile, the stretchout for the wire blank, Fig. 58, can be determined in the usual manner.

22. Related Mathematics on Painter's Pail.—Volume of a Cylinder.—The volume of a cube is equal to the length of the base, times the width of the base, times the height of the cube. This is written $$\scriptstyle{V=L\times W\times H}$$. It has also been found that length times width gives the area. Because of this it can be said that volume equals area times height, and that the volume of a cylinder is equal to the area of the base times the height. The base of a cylinder is a circle, the area of which equals D$2$×.7854. Therefore, for a cylinder, Volume equals Diameter squared times .7854 times the height, or $$\scriptstyle{V=D^2\times.7854\times H}$$.

Sample Problem.—Find the volume of a cylinder 4&Prime; in diameter and 6&Prime; high. Problem 7A.—Compute the volume of the Painter's Pail, Figs. 52 and 53.

Cubic Inches in One Gallon.—It is established by law that one gallon of liquid measure shall contain 231 cubic inches.

Problem 7B.—How many cubic inches are there in one quart? In one pint?

Problem 7C.—What is the exact capacity of the pail. Fig. 53, in quarts and fractional parts of a quart?

Problem 7D.—If a job called for a pail 8&Prime; in diameter and 7¼&Prime; high, what would be its exact capacity in quarts?