A finger is a natural 1, and 45 is 2deci, thus your hands make a natural decimal-base. Note that when you tried to show base-(9+2), you made a mistake in count

A finger is a natural 1, and 45 is 2deci, thus your hands make a natural decimal-base. Note that when you tried to show base-(9+2), you made a mistake in counting. It looks like you treated "all fingers" as 9+2, and "all but one fingers" as 9. That's inconsistent. Unless you have 6 fingers on one hand?