They only apply accurately to divisions by 2, 4, 5, 10, 20, 25 or 50; but they have the convenience of fitting in with the denary scale of notation, and they can be extended to other divisions by using a mixed number as numerator.
This linguistic poverty proves that the Australian tongue has no affinity to the Polynesian group of languages, where denary enumeration prevails: the nearest Polynesians, the Maoris, counting in thousands.
In other words, the denary scale, though adopted in notation and in numeration, does not arise in the corresponding mental concept until we get beyond too.
In consequence of this limitation of the power of perception of number, it is practically impossible to use a pure denary scale in elementary number-teaching.
Within each denomination, however, the denary notation is employed exclusively, e.g.
Finger-counting is of course natural to children, and leads to grouping into fives, and ultimately to an understanding of the denary system of notation.
The words eleven and twelve have been supposed to suggest etymologically a denary basis (see, however, Numeral) .
There is no essential difference, however, between this and the denary basis.
The numeration was in the denary scale, so that it did not agree absolutely with the notation.