[16] The method of solving this and the following question may be shewn thus: If the number of days in which each could reap the field is given, the part which each could do in a day by himself can be found, and thence the part which all could do together; this being known, the number of days which it would take all to do the whole can be found.
[17] A formula is a name given to any algebraical expression which is commonly used.
[18] Or remove ciphers from the divisor; or make up the number of ciphers partly by removing from the divisor and annexing to the dividend, if there be not a sufficient number in the divisor.
[19] These are not quite correct, but sufficiently so for every practical purpose.
[20] The 1′ here means that the 1 is in the multiplier.
[21] This is written 7 instead of 6, because the figure which is abandoned in the dividend is 9 (151).
[22] Meaning, of course, a really fractional number, such as ⅞ or ¹⁵/₁₁, not one which, though fractional in form, is whole in reality, such as ¹⁰/₅ or ²⁷/₃.
[23] By square number I mean, a number which has a square root. Thus, 25 is a square number, but 26 is not.
[24] The term ‘root’ is frequently used as an abbreviation of square root.
[25] Or, more simply, add the second figure of the root to the first divisor.