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Rh that of double foolscap 459 square inches. For approximate purposes these may be taken as 350 and 460, and this shows large post to be practically three-quarters of the area of double foolscap. Other instances may be cited: demy 393¾ square inches, if taken as 400, renders royal as one-fourth extra, and double crown one-half above the demy weights. These figures are useful for quick calculation, but the first method is more exact and should be generally adopted.

To find the Number of Sheets which a Reel of Paper will Produce.—Weigh the reel and deduct the weight of the core or centre. Cut a piece the full size of the sheet, but if a trim is allowed, the sheet cut should be untrimmed size. Weigh the sheet on the sheet scale, read the weight in 500's, and divide the weight given into the net weight of the reel, and multiply the result by 500, this giving the number of sheets which will be produced.

Example.—Reel is 50 inches wide, weighs 740 lb.; the centre is 10 lb. in weight; to be cut to sheet 25 by 20 inches.

Sheet 25 by 20 inches = 25 lb. per 500.

Alternatively a square may be cut by the demy template, weighed on the demy scale, the weight of the sheet equivalent to the demy weight calculated or obtained from table, and the number of sheets obtained as in above example.

Example.—Reel is 48 inches wide, weighs 640 lb. with 4 lb. centre; to be cut to 24 by 36 inches; demy = 21 lb. per 500 sheets.

To find the Number of Copies of a Book that may be Obtained from a Given Quantity of Paper.—A publisher sends in twenty-seven perfect reams of quad crown for a crown octavo work of 216 pages. How many copies will be produced? A sheet of crown octavo = 16 pages, therefore quad crown = 64 pages.