is turned up in the "thin edge" and is "snapped on" over the lower edge of the body. The profile of the handle is shown in elevation. This profile is divided into equal spaces. This spacing is transferred to any straight line and perpendiculars erected at the first and last points. Using the line of stretchout as a center line, ¼ in. is set off on each side for the width of the top and ⅛ in. on each side for the width of the bottom. The pattern of the handle is completed by connecting these points with straight lines. The handle is intended to be made from No. 20 gage iron, tinned. Should the handle be made from lighter material, it would be necessary to add a hem to the long sides of the pattern in order to gain the necessary rigidity.
20. Related Mathematics on Half-pint Cup.—Problem 6A.—How many sheets of tin plate measuring 20″×28″ would be required to make fifty half-pint cups? Treat the bottom of the cup as a square piece of metal.
Problem 6B.—What would be the percentage of waste for the entire job?
Problem 6C.—20″×28″ IX "Charcoal Tin, Bright" is packed by the manufacturers in boxes containing 112 sheets. If this grade of tin plate is selling for $26 per box, how much will the tin required for fifty half-pint cups (Problem 6A) cost?
Area of a Circle.—The method of calculating the area of a circle will be thoroughly understood by the student if he will go through the following exercise:
Draw a 5″ square. Draw straight lines connecting opposite corners of this square. These lines are called the diagonals of the square. The diagonals of a square, or rectangle, always divide each other into two equal parts. Using the point where the diagonals cross each other (intersect) as a center, draw a circle that will just touch the center of each side of the square. What is the diameter of this circle? How does this diameter compare with the length of the sides of the square? You have drawn what is known as an inscribed circle; that is, a circle whose circumference touches all sides of the containing figure but does not pass beyond the sides. What is the area of this square? Would you get the same answer if you simply multiplied the diameter by itself? This operation is known as "squaring the diameter" and is always written D2. Look up a table of areas of circles and you will find the area of a 5″ circle given as 19.635″. Now, divide the
