Elementary arithmetic, with brief notices of its history... by Robert Potts.

27

Each different system of arithmetical notation admits of fractions
analogous to decimal fractions as well as ordinary fractions. All other
scales of notation except the denary, are for the most part subjects of
curiosity rather than utility, yet not altogether useless from an intellectual point of view, as they supply instances of the application and
extension of a general principle.
It may however be noted, that the duodenary scale is sometimes
employed for finding, by means of the duodecimal division of the
foot, the areas of surfaces and the volumes of solids.
It is obvious that the digits 3, 5, 4, 2, will be found by successively dividing
1304 by the local value 7.
7)1304
7)186-2
7)26-4
7)3-5
0-3
And 1304 in the denary = 3542 in the septenary scale.
Ex. To find the sum of 2345 and 7164, and the difference of 3542 arnd 1161 in the
septenary scale: -
2345 3542
1164 1164
3542 sum. 2345 difference.
To find the product of 3542 and 1164; and the quotient of 4566111 divided by
1161 in the septenary scale:3542 1164)4566111(3542 quotient.
1164 3555
21131 10111
31545 6246
3542 5321
3542 5052
4566111 product 61
2361
236