Number Base Notation
Why
In our definition of natural number notation,
the notation $(\eta _1, \eta _2, \eta _3)$, which
we agreed to denote $\eta _3\eta _2\eta _1$ has
the corresponding number
\[
\eta _1 + \eta _2\cdot 10 + \eta _3\cdot (10^2)
\] \[
\sum_{i = 1}^{k} \eta _k \cdot (10)^{k-1}
\]