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Rh sides as indicated. The bottom corners of the end pattern are notched straight across. The single and double edge notches should be dropped below the bending line at the top of the pan a distance equal to the diameter of the wire. This will allow the wire to lay against the pan instead of riding over the double seams.

All necessary dimensions should be placed on the front and end elevations and the over-all dimensions on the pattern.

16. Related Mathematics on Iron Bread Pan.—Trapezoid.—A trapezoid is a flat surface bounded by four straight lines only two of which are parallel. The parallel sides are known as the upper and lower bases of the trapezoid.

The area of a trapezoid is equal to one-half the sum of the bases multiplied by the altitude. The altitude of any surface is always the shortest distance between its upper and lower parts. The altitude must always be measured at right angles to the lower base.

Problem 4A.—How many body blanks, Fig. 34, can be cut from a sheet of black iron 30" wide and 96" long? Treat the pattern as a rectangle using the over-all dimensions.

Problem 4B.—Could any of the pieces left from the body blanks be used for end blanks? If so, how many end blanks could be obtained from these?

Problem 4C.—What is the total area of the waste pieces?

Problem 4D.—What is the percentage of waste for one body blank?

Problem 4E.—By reversing the end pattern when laying out on the sheets some material may be saved. Show by a sketch how to effect this saving of material from a 30"×96" sheet. How many end blanks can be obtained from one of these sheets?

Problem 4F.—What is the total area of the waste pieces from one of the above sheets?

Problem 4G.—What is the area of one end blank? What is the percentage of waste?

Problem 4H.—The bread pans are to be made of No. 28 black iron weighing .625 lb. per sq. ft. How much will 1000 body patterns weigh after corrections are made for waste? How much will 2000 end patterns weigh after corrections are made for waste? What will be the correct weight of 1000 of these pans?