MOHAMMED BEN MUSA’S
COMPENDIUM
on calculating by
COMPLETION AND REDUCTION.
(3) When I considered what people generally want in calculating, I found that it always is a number.
I also observed that every number is composed of units, and that any number may be divided into units.
Moreover, I found that every number, which may be expressed from one to ten, surpasses the preceding by one unit: afterwards the ten is doubled or tripled, just as before the units were: thus arise twenty, thirty, &c., until a hundred; then the hundred is doubled and tripled in the same manner as the units and the tens, up to a thousand; then the thousand can be thus repeated at any complex number; and so forth to the utmost limit of numeration.
I observed that the numbers which are required in calculating by Completion and Reduction are of three kinds, namely, roots, squares, and simple numbers relative to neither root nor square.
