Page:The Algebra of Mohammed Ben Musa (1831).djvu/74

 If the instance be: “To find a number, one-third of which, when multiplied by one-fourth of it, restores the number,” then the computation is: You multiply one-third of thing by one-fourth of thing, this gives one-twelfth of a square, equal to thing, and the square is equal to twelve things, which is the root of one hundred and forty-four.

If the instance be: “A number, one-third of which and one dirhem multiplied by one-fourth of it and two dirhems restore the number, with a surplus of thirteen dirhems;” then the computation is this: You multiply one-third of thing by one-fourth of thing, this gives half one-sixth of a square; and you multiply two dirhems by one-third of thing, this gives two-thirds of a root; and one dirhem by one-fourth of thing gives one-fourth of a root; and one dirhem by two dirhems gives two dirhems. This altogether is one-twelfth of a square and two dirhems and eleven-twelfths of a thing, equal to thing and thirteen dir-