Determining the correct total issue size when shares are divided among three groups and the counts are commensurable (Mutawaafiqah)?
Chapter on the Roots of Inheritance Shares that Increase (Awl)
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
When the three counts are commensurable (share a common factor), the fraction (Wifq) of one count is multiplied by the entirety of the second count. This intermediate result is then reconciled with the third count, and its fraction is multiplied by the entirety of the third count. The final result is then multiplied by the original base of the shares to establish the corrected total issue size. If two counts are identical and the third is disparate or commensurable, one of the identical counts is multiplied by the entirety of the third count, or by its fraction if it is commensurable. This result is then multiplied by the original base.
Supporting text
If two counts are proportional and the third is disparate, the largest of the two proportional counts is multiplied by the entirety of the third count, or by its fraction if it is commensurable, and this result is then multiplied by the original base. If two counts are commensurable and the third is disparate, the fraction of one commensurable count is multiplied by the entirety of the other, and this result is then multiplied by the third count before multiplying by the original base.