the Basrans, which is to 'stop' one of the three, find the concordance between it and the other two, and reduce them to their concordant parts. Then, you look at the two concordant parts; if they are identical, you multiply one of them by the 'stopped' number. If they are proportional, you multiply the larger of them, and if they are disparate, you multiply one by the other and then by the 'stopped' number. If they are concordant, you multiply the concordant part of one of them by the entirety of the other, then by the 'stopped' number. Whatever amount is reached, you multiply it by the issue. An example of this is: ten grandmothers, twelve paternal uncles, and fifteen daughters. So, 'stop' the ten; the twelve are concordant with it by a half, so they reduce to six, and the fifteen are concordant with it by fifths, so they reduce to three. The latter is contained within the six, so you multiply the six by the ten, resulting in sixty, then by the issue, resulting in three hundred and sixty. If you 'stop' the twelve, the ten reduces to its half, five, and the fifteen to its third, five, and since they are identical, you multiply five by twelve, resulting in sixty. If you 'stop' the fifteen, the ten reduces to two, and the twelve to four; since the two is contained within the four, you multiply that by the fifteen, resulting in sixty, then by the issue.

Section: On knowing concordance, proportionality, and disparity. The method for this is to remove the smaller of the two numbers from the larger one, time after time. If it is exhausted by it, the two numbers are proportional. If it is not exhausted by it, but there remains a remainder, you remove it from the smaller number. If a remainder remains from that, you remove it from the first remainder. You continue in this manner, removing each remainder from the one before it, until you arrive at a number by which the number removed is exhausted, other than one. Whichever remainder exhausts it—other than one—the concordance between the two numbers is by that fraction. If that remainder is two, it is by halves; if it is three, by thirds; if it is four, by fourths; if it is eleven, twelve, or thirteen, that is categorized accordingly. If one remains, the two numbers are disparate. What indicates to you the proportionality of two numbers is that whenever you increase...