(Sheet dimen.) X Basis wt. / (Area of basic size) = Rounded ream wt. X 2 = M-Weight
The M-weight of a sheet of 11×17” book paper with a basis weight of 70 lbs. is: (11×17) X 70 / (25×38) = 13.78 X 2 = 27.56
The area of the given sheet size is 11 x 17 = 187 inches². Since this is less than 336 inches², ream weight should be rounded to the nearest hundredth of a pound.