Page:Sheet Metal Drafting.djvu/208

194 Problem 47C.—A furnace man finds the following sizes of oval risers have been installed in the partitions: One 3½"×13⅝"; one 6"×9¼"; one 3½"×15⅛"; and one 3½"×14¼". What are the equivalent round pipe areas for cellar mains to supply each of these risers? What is the nearest diameters of the cellar mains if the diameters increase by half inches?