[39] For a square, the length of the perpendicular is ⅛th the exterior side; for a pentagon ⅐th; for the hexagon, and other polygons, ⅙th.
[40] Vide [Tables of Weights, and Measures].
[41] [Vide Tables of Weights, and Measures].
[42] In reducing fractions to a common denominator, and in multiplication of fractions, the work may be considerably diminished by cancelling any figures, which are in all the multiples; or by dividing a figure in each of them by any figure which can divide all without any remainder.
[43] See [Note], [page 268].
[44] To multiply decimals by 1, with any number of ciphers, as 10, 100, &c.—This is done by only removing the decimal point so many places farther to the right hand, as there are ciphers in the multiplier, and subjoining ciphers, if need be.
[45] The best way of doubling the root, to form the new divisor, is by adding the last figure always to the last divisor, as appears in the following example.
After the figures belonging to the given number are all exhausted, the operation may be continued into decimals, by adding any number of periods of ciphers, two in each period.
[46] This rule is only applicable to the very best-made new cordage. The circumference squared should be divided by 6 instead of 5 for the description of rope generally employed.
[47] When the board is tapering, add the breadths at the two ends together, and take half the sum for the mean breadth. Or else, take the mean breadth in the middle.